Spherical zone seal body

ABSTRACT

A spherical annular seal member ( 58 ) includes: a spherical annular base member ( 56 ) defined by a cylindrical inner surface ( 52 ), a partially convex spherical surface ( 56 ), and end faces ( 54, 55 ); and an outer layer ( 57 ) formed integrally with the partially convex spherical surface ( 53 ) of the spherical annular base member ( 56 ). The spherical annular base member ( 56 ) includes a reinforcing member ( 5 ) made from a compressed metal wire net ( 4 ) and a heat-resistant material filling meshes of the metal wire net ( 4 ) of the reinforcing member ( 5 ), integrated with the reinforcing member ( 5 ) in mixed form, and containing expanded graphite and an organic phosphorus compound. The outer layer ( 56 ) includes a heat-resistant material constituted by a heat-resistant sheet member ( 6 ) containing expanded graphite and an organic phosphorus compound, and a reinforcing member constituted by a metal wire net ( 4 ) integrated with the heat-resistant material in mixed formed.

TECHNICAL FIELD

The present invention relates to a spherical annular seal member used ina spherical pipe joint for an automobile exhaust pipe.

BACKGROUND ART

A conventional spherical annular seal member used in a spherical pipejoint for an automobile exhaust pipe is heat resistant, excels inaffinity with a mating member, and has remarkably improved impactstrength, but has a drawback in that the seal member often generatesabnormal noise when it undergoes friction under dry frictionalconditions (published in JP-A-54-76759). The drawback of this sealmember is conceivably attributable to, among others, the fact that thereis a large difference between the coefficient of static friction and thecoefficient of dynamic friction of a heat-resistant material (such asexpanded graphite) for forming the seal member, and to the fact that theseal member constituted by this heat-resistant material exhibitsnegative resistance with respect to the sliding velocity or speed.

Therefore, to overcome the above-described drawback, the presentapplicant proposed a seal member which excels in the sealingcharacteristic without generating abnormal frictional noise in thesliding on a mating member, and satisfies the performance required of aseal member (Japanese Patent No. 3,139,179).

However, with respect to this proposed seal member as well, a newproblem has been presented which is attributable to, among others, theimprovement in recent years of the performance of automobile engines.That is, the conventional seal members are unable to satisfy theconditions of use in the light of heat resistance, owing to an increasein the exhaust-gas temperature due to the improved performance of theautomobile engines, or owing to an increase in the exhaust-gastemperature attributable to the fact that the spherical pipe joint islocated closer to the engine side in a case where the spherical pipejoint is disposed in the vicinity of an outlet (manifold) of the exhaustgases, for the purpose of improving the noise, vibration and harshness(NVH) characteristics of an automobile. Thus, there has been acompelling need for improvement of the heat resistance of the sealmember itself.

With respect to the above-described newly presented problem, the presentapplicant proposed spherical annular seal members and methods ofmanufacturing the same in which heat resistance is improved(JP-A-10-9396 and JP-A-10-9397).

The above-described spherical annular seal members are capable ofsuppressing the oxidative wear to low levels, do not generate abnormalfrictional noise, excel in sealing characteristics, and are capable ofsatisfying their functions as seal members even under high temperaturesof 600° C. to 700° C. However, in the case of these spherical annularseal members, since a heat-resistant sheet member, e.g., aheat-resistant sheet member having on the surfaces of an expandedgraphite sheet a heat-resistant coating formed of heat-resistantmaterials, is used in the manufacturing methods, the flexibilityinherent in the expanded graphite sheet is sacrificed. In consequence,there are possibilities that the cracking, breakage, and the like of theheat-resistant coating and, hence, the breakage and the like of theheat-resistant sheet member can often occur in the bending operation andthe like involved in the process of manufacturing the spherical annularseal member. Thus, it was found that there is room for improvement interms of the material yield, and that the elimination of the drawback ofthe material yield has the advantage of shortening the process ofmanufacturing the spherical annular seal member, leading to thereduction of the manufacturing cost.

DISCLOSURE OF THE INVENTION

The present invention has been devised in view of the above-describedaspects, and its object is to provide a spherical annular seal memberwhich exhibits performance equivalent to that of the spherical annularseal members of the above-described prior art in that the sphericalannular seal member has heat resistance (resistance to oxidative wear),does not generate abnormal frictional noise, and excels in the sealingcharacteristic even in a high-temperature range exceeding 700° C., andwhich, in its manufacturing method, is capable of overcoming thedrawback of the material yield of the heat-resistant sheet member and oflowering the manufacturing cost.

A spherical annular seal member in accordance with a first aspect of thepresent invention is a spherical annular seal member which is usedparticularly in an exhaust pipe spherical joint, comprising: a sphericalannular base member defined by a cylindrical inner surface, a partiallyconvex spherical surface, and large- and small-diameter-side annular endfaces of the partially convex spherical surface; and an outer layerformed integrally with the partially convex spherical surface of thespherical annular base member, wherein the spherical annular base memberincludes a reinforcing member made from a compressed metal wire net anda heat-resistant material filling meshes of the metal wire net of thereinforcing member, compressed in such a manner as to be formedintegrally with the reinforcing member in mixed form, and containingexpanded graphite and an organic phosphorus compound, the outer layerincludes a heat-resistant material containing expanded graphite and anorganic phosphorus compound, and a reinforcing member constituted by ametal wire net integrated with the heat-resistant material in mixedformed, and an outer surface of the partially convex spherical surfaceexposed to an outside in the outer layer is formed into a smooth surfacein which the heat-resistant material and the reinforcing member areintegrated in mixed form.

In accordance with the spherical annular seal member according to thefirst aspect, the spherical annular base member defined by thecylindrical inner surface, the partially convex spherical surface, andthe large- and small-diameter-side annular end faces of the partiallyconvex spherical surface includes a reinforcing member made from acompressed metal wire net and a heat-resistant material filling meshesof the metal wire net of the reinforcing member, compressed in such amanner as to be formed integrally with the reinforcing member in mixedform, and containing expanded graphite and an organic phosphoruscompound. Therefore, the oxidative wear of expanded graphiteconstituting a principal ingredient of the heat-resistant material isreduced even in a high-temperature range exceeding 700° C. by virtue ofthe oxidation suppressing action of the organic phosphorus compound,with the result that the heat resistance of the spherical annular sealmember improves.

In addition, the outer layer includes a heat-resistant materialcontaining expanded graphite and an organic phosphorus compound, and areinforcing member constituted by a metal wire net integrated with theheat-resistant material in mixed formed, and an outer surface of thepartially convex spherical surface exposed to an outside in the outerlayer is formed into a smooth surface in which the heat-resistantmaterial and the reinforcing member are integrated in mixed form.Therefore, the oxidative wear of expanded graphite constituting theprincipal ingredient of the heat-resistant material is reduced even in ahigh-temperature range exceeding 700° C. by virtue of the oxidationsuppressing action of the organic phosphorus compound. Hence, in thesliding contact with a mating member, the formation of an excess coatingof the heat-resistant material which forms an outer surface layer on thesurface of the mating member is suppressed, and smooth sliding contactwith the surface of the mating member is effected.

A spherical annular seal member in accordance with a second aspect ofthe present invention is a spherical annular seal member which is usedparticularly in an exhaust pipe spherical joint, comprising: a sphericalannular base member defined by a cylindrical inner surface, a partiallyconvex spherical surface, and large- and small-diameter-side annular endfaces of the partially convex spherical surface; and an outer layerformed integrally with the partially convex spherical surface of thespherical annular base member, wherein the spherical annular base memberincludes a reinforcing member made from a compressed metal wire net anda heat-resistant material filling meshes of the metal wire net of thereinforcing member, compressed in such a manner as to be formedintegrally with the reinforcing member in mixed form, and containingexpanded graphite and an organic phosphorus compound, the outer layerincludes a lubricating composition constituted of at least boron nitrideand at least one of alumina and silica, and a reinforcing memberconstituted by a metal wire net integrated with the lubricatingcomposition in mixed formed, and an outer surface of the partiallyconvex spherical surface exposed to an outside in the outer layer isformed into a smooth lubricating sliding surface in which thelubricating composition and the reinforcing member are integrated inmixed form.

In accordance with the spherical annular seal member according to thesecond aspect, the spherical annular base member defined by thecylindrical inner surface, the partially convex spherical surface, andthe large- and small-diameter-side annular end faces of the partiallyconvex spherical surface includes a reinforcing member made from acompressed metal wire net and a heat-resistant material filling meshesof the metal wire net of the reinforcing member, compressed in such amanner as to be formed integrally with the reinforcing member in mixedform, and containing expanded graphite and an organic phosphoruscompound. Therefore, the oxidative wear of expanded graphiteconstituting the principal ingredient of the heat-resistant material isreduced even in a high-temperature range exceeding 700° C. by virtue ofthe oxidation suppressing action of the organic phosphorus compound,with the result that the heat resistance of the spherical annular sealmember improves.

The outer layer includes a lubricating composition constituted of atleast boron nitride and at least one of alumina and silica, and areinforcing member constituted by a metal wire net integrated with thelubricating composition in mixed formed, and an outer surface of thepartially convex spherical surface exposed to an outside in the outerlayer is formed into a smooth lubricating sliding surface in which thelubricating composition and the reinforcing member are integrated inmixed form. Therefore, smooth sliding movement is effected in thesliding contact with a mating member.

As for the spherical annular seal member according to a third aspect ofthe invention, in the spherical annular seal member according to thesecond aspect, the lubricating composition contains 70-90 wt. % of boronnitride and 10-30 wt. % of at least one of alumina and silica.

In accordance with the spherical annular seal member according to thethird aspect, the partially convex spherical outer surface in the outerlayer of the lubricating composition containing 70-90 wt. % of boronnitride and 10-30 wt. % of at least one of alumina and silica is formedinto a smooth surface in which the reinforcing member constituted by themetal wire net integrated with the lubricating composition in mixed formis exposed. Therefore, smooth sliding movement is effected particularlyin the initial sliding movement with respect to the mating member, andthe generation of abnormal noise in sliding friction which occasionallyoccurs in the initial period of sliding can be prevented.

As for the spherical annular seal member according to a fourth aspect ofthe invention, in the spherical annular seal member according to thesecond or third aspect, the lubricating composition further containspolytetrafluoroethylene resin.

As for the spherical annular seal member according to a fifth aspect ofthe invention, in the spherical annular seal member according to any oneof the second to fourth aspects, the lubricating composition contains amixture consisting of 70-90 wt. % of boron nitride and 10-30 wt. % of atleast one of alumina and silica, and further contains not more than 200parts by weight of polytetrafluoroethylene resin with respect to 100parts by weight of the mixture.

As for the spherical annular seal member according to a sixth aspect ofthe invention, in the spherical annular seal member according to any oneof the second to fourth aspects, the lubricating composition contains amixture consisting of 70-90 wt. % of boron nitride and 10-30 wt. % of atleast one of alumina and silica, and further contains 50 to 150 parts byweight of polytetrafluoroethylene resin with respect to 100 parts byweight of the mixture.

In accordance with the spherical annular seal member according to anyone of the fourth, fifth, and sixth aspects, the partially convexspherical outer surface in the outer layer of the lubricatingcomposition further containing polytetrafluoroethylene resin is formedinto a smooth surface in which the reinforcing member constituted by themetal wire net integrated with the lubricating composition in mixed formis exposed. Therefore, smooth sliding movement is effected particularlyin the initial sliding movement with respect to the mating member, andthe generation of abnormal noise in sliding friction which occasionallyoccurs in the initial period of sliding can be prevented.

As for the spherical annular seal member according to a seventh aspectof the invention, in the spherical annular seal member according to anyone of the first to sixth aspects, the heat-resistant materialcontaining the expanded graphite and the organic phosphorus compound ofthe spherical annular base member is exposed on the cylindrical innersurface.

In accordance with the spherical annular seal member according to theseventh aspect, the oxidative wear of expanded graphite constituting theprincipal ingredient of the heat-resistant material in the cylindricalinner surface is reduced by virtue of the oxidation suppressing actionof the organic phosphorus compound, with the result that the heatresistance of the spherical annular seal member improves. In addition,when the spherical annular seal member is fitted and fixed to the outersurface of the exhaust pipe, sealability between the cylindrical innersurface of the spherical annular seal member and the outer surface ofthe exhaust pipe is increased, so that leakage of exhaust gases from thecontact surfaces can be prevented as practically as possible.

As for the spherical annular seal member according to an eighth aspectof the invention, in the spherical annular seal member according to anyone of the first to seventh aspects, the reinforcing member constitutedby the metal wire net of the spherical annular base member is exposed onthe cylindrical inner surface.

In accordance with the spherical annular seal member according to theeighth aspect, when the spherical annular seal member is fitted andfixed to the outer surface of the exhaust pipe, friction between thecylindrical inner surface and the outer surface of the exhaust pipe isincreased, with the result that the spherical annular seal member isfirmly fixed to the outer surface of the exhaust pipe.

As for the spherical annular seal member according to a ninth aspect ofthe invention, in the spherical annular seal member according to any oneof the first to eighth aspects, the heat-resistant material containingthe expanded graphite and the organic phosphorus compound of thespherical annular base member is exposed on at least one of the annularend faces.

In accordance with the spherical annular seal member according to theninth aspect, the oxidative wear of expanded graphite constituting theprincipal ingredient of the heat-resistant material in the annular endfaces is reduced by virtue of the oxidation suppressing action of theorganic phosphorus compound, with the result that the heat resistance ofthese annular end faces improves.

As for the spherical annular seal member according to a 10th aspect ofthe invention, in the spherical annular seal member according to any oneof the first to ninth aspects, the heat-resistant material contains 0.1to 10.0 wt. % of the organic phosphorus compound and 90.0 to 99.9 wt. %of the expanded graphite.

In accordance with the spherical annular seal member according to the10th aspect, the heat-resistant material contains in a proportion of 0.1to 10.0 wt. % the organic phosphorus compound necessary for favorablydemonstrating the oxidation suppressing action with respect to theexpanded graphite constituting the principal ingredient. Therefore, theoxidative wear of the expanded graphite is favorably reduced, and theweight loss of the spherical annular seal member ascribable to theoxidative wear of the expanded graphite is favorably reduced.

If the content of the organic phosphorus compound is less than 0.1 wt.%, the effect is not favorably exhibited on the oxidation suppressingaction with respect to the expanded graphite. Meanwhile, if the organicphosphorus compound is contained in excess of 10.0 wt. %, any furthereffect on the oxidation suppressing action is not favorably exhibited.In addition, there is a possibility of impairing the flexibility of theexpanded graphite sheet as the heat-resistant material, and the breakageor the like of the expanded graphite sheet occurs occasionally in thebending process or the like in the process of manufacturing thespherical annular seal member.

As in the spherical annular seal member according an 11th aspect of theinvention, the organic phosphorus compound for favorably reducing theoxidative wear of the expanded graphite is selected from the groupconsisting of an organic phosphonic acid or an ester thereof, an organicphosphinic acid or an ester thereof, a phosphoric ester, a phosphorousester, and a hypophosphorous ester.

As in the spherical annular seal member according a 12th aspect of theinvention, the organic phosphonic acid or the ester thereof representedby the following general formula (1) is used:

wherein R¹ is an alkyl group having a carbon number of 1 to 10, an arylgroup having a carbon number of 6 to 18, or an aralkyl group consistingof an alkylene portion having a carbon number of 1 to 10 and an arylportion having a carbon number of 6 to 18, and each of R and R³ is ahydrogen atom, an alkyl group having a carbon number of 1 to 10, an arylgroup having a carbon number of 6 to 18, or an aralkyl group consistingof an alkylene portion having a carbon number of 1 to 10 and an arylportion having a carbon number of 6 to 18.

As in the spherical annular seal member according a 13th aspect of theinvention, the organic phosphinic acid or the ester thereof representedby the following general formula (2) is used:

wherein R⁴ is an alkyl group having a carbon number of 1 to 10, an arylgroup having a carbon number of 6 to 18, or an aralkyl group consistingof an alkylene portion having a carbon number of 1 to 10 and an arylportion having a carbon number of 6 to 18, and each of R⁵ and R⁶ is ahydrogen atom, an alkyl group having a carbon number of 1 to 10, an arylgroup having a carbon number of 6 to 18, or an aralkyl group consistingof an alkylene portion having a carbon number of 1 to 10 and an arylportion having a carbon number of 6 to 18.

As in the spherical annular seal member according a 14th aspect of theinvention, the phosphoric ester represented by the following generalformula (3) is used:

wherein each of R⁷, R⁸, and R⁹ is a hydrogen atom, an alkyl group havinga carbon number of 1 to 10, an aryl group having a carbon number of 6 to18, or an aralkyl group consisting of an alkylene portion having acarbon number of 1 to 10 and an aryl portion having a carbon number of 6to 18, providing that a case where all of them are hydrogen atoms isexcluded.

As in the spherical annular seal member according a 15th aspect of theinvention, the phosphorous ester is used by being selected from aphosphorous triester represented by the following general formula (4)and a phosphorous diester or a phosphorous monoester represented by thefollowing general formula (5):

wherein each of R¹⁰, R¹¹, and R¹² is an alkyl group having a carbonnumber of 1 to 10, an aryl group having a carbon number of 6 to 18, oran aralkyl group consisting of an alkylene portion having a carbonnumber of 1 to 10 and an aryl portion having a carbon number of 6 to 18,and each of R¹³ and R¹⁴ is a hydrogen atom, an alkyl group having acarbon number of 1 to 10, an aryl group having a carbon number of 6 to18, or an aralkyl group consisting of an alkylene portion having acarbon number of 1 to 10 and an aryl portion having a carbon number of 6to 18, providing that a case where both of R¹³ and R¹⁴ are hydrogenatoms is excluded.

As in the spherical annular seal member according a 16th aspect of theinvention, as the hypophosphorous ester, a hypophosphorous diester(phosphonite) represented by the following general formula (6) or ahypophosphorous monoester represented by the following general formula(7) is used:

wherein R¹⁵ is a hydrogen atom, an alkyl group having a carbon number of1 to 10, an aryl group having a carbon number of 6 to 18, or an aralkylgroup consisting of an alkylene portion having a carbon number of 1 to10 and an aryl portion having a carbon number of 6 to 18, and each ofR¹⁶, R¹⁷, and R¹⁸ is an alkyl group having a carbon number of 1 to 10,an aryl group having a carbon number of 6 to 18, or an aralkyl groupconsisting of an alkylene portion having a carbon number of 1 to 10 andan aryl portion having a carbon number of 6 to 18.

In the spherical annular seal member in accordance with the invention,the spherical annular base member includes the reinforcing member madefrom a compressed metal wire net and the heat-resistant material fillingmeshes of the metal wire net of the reinforcing member, compressed insuch a manner as to be formed integrally with the reinforcing member inmixed form, and containing expanded graphite and an organic phosphoruscompound. Since the heat resistance of the seal member itself isincreased, it is possible to suppress to a low level the rate of weightloss due to the oxidative wear of the expanded graphite making up thespherical annular seal member, and it is possible to sufficientlyexhibit the function as the spherical annular seal member and improvethe durability of the spherical annular seal member. In addition, sincethe heat-resistant sheet member containing the expanded graphite and theorganic phosphorus compound has flexibility which the ordinary expandedgraphite sheet has, no problem occurs in the bending process of theheat-resistant sheet member which is carried out in the process ofmanufacturing the spherical annular seal member. This makes it possibleto not only eliminate the process of forming a coating of theheat-resistant material on the surface of the expanded graphite sheet inthe conventional technique, but also prevent the fracture of theheat-resistant coating occurring in the bending process of the expandedgraphite sheet having the heat-resistant coating and, hence, thebreakage of the expanded graphite sheet, consequently leading to theimprovement of the material yield.

Hereafter, a detailed description will be given of the present inventionand its embodiments. It should be noted that the present invention isnot limited to these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view illustrating a sphericalannular seal member in accordance with the present invention;

FIG. 2 is a diagram explaining a method of forming a reinforcing memberin a process of manufacturing the spherical annular seal member inaccordance with the present invention;

FIG. 3 is a perspective view of a heat-resistant sheet member in theprocess of manufacturing the spherical annular seal member in accordancewith the present invention;

FIG. 4 is a perspective view of a superposed assembly in the process ofmanufacturing the spherical annular seal member in accordance with thepresent invention;

FIG. 5 is a plan view illustrating a tubular base member in the processof manufacturing the spherical annular seal member in accordance withthe present invention;

FIG. 6 is a vertical cross-sectional view of the tubular base membershown in FIG. 5;

FIG. 7 is a perspective view of a heat-resistant sheet member in theprocess of manufacturing the spherical annular seal member in accordancewith the present invention;

FIG. 8 is a diagram explaining a method of forming anouter-surface-layer forming member in the process of manufacturing thespherical annular seal member in accordance with the present invention;

FIG. 9 is a diagram explaining a method of forming theouter-surface-layer forming member in the process of manufacturing thespherical annular seal member in accordance with the present invention;

FIG. 10 is a plan view illustrating a cylindrical preform in the processof manufacturing the spherical annular seal member in accordance withthe present invention;

FIG. 11 is a vertical cross-sectional view illustrating a state in whichthe cylindrical preform is inserted in a die in the process ofmanufacturing the spherical annular seal member in accordance with thepresent invention;

FIG. 12 is a vertical cross-sectional view of the heat-resistant sheetmember forming a lubricating sliding layer in the process ofmanufacturing the spherical annular seal member in accordance with thepresent invention;

FIG. 13 is a diagram explaining a method of forming theouter-surface-layer forming member in the process of manufacturing thespherical annular seal member in accordance with the present invention;

FIG. 14 is a diagram explaining a method of forming theouter-surface-layer forming member in the process of manufacturing thespherical annular seal member in accordance with the present invention;

FIG. 15 is a plan view illustrating the cylindrical preform in theprocess of manufacturing the spherical annular seal member in accordancewith the present invention;

FIG. 16 is a vertical cross-sectional view illustrating a sphericalannular seal member in accordance with the present invention;

FIG. 17 is a partially enlarged cross-sectional view illustrating theouter surface, formed in the shape of the partially convex sphericalsurface, of the spherical annular seal member shown in FIG. 1; and

FIG. 18 is a vertical cross-sectional view of an exhaust pipe sphericaljoint in which the spherical annular seal member in accordance with thepresent invention has been incorporated.

BEST MODE FOR CARRYING OUT THE INVENTION

A description will be given of the constituent materials of a sphericalannular seal member in accordance with the invention and a method ofmanufacturing the spherical annular seal member.

<Concerning Heat-Resistant Sheet Member>

<Manufacturing Method: I>

While 300 parts by weight of concentrated sulfuric acid of a 98%concentration is being agitated, 5 parts by weight of a 60% aqueoussolution of hydrogen peroxide is added to it as an oxidizing agent, andthis solution is used as a reaction solution. This reaction solution iscooled and kept at a temperature of 10° C., 100 parts by weight ofnatural flake graphite powder having a particle size of 30 to 80 meshesis added to it, and reaction is allowed to take place for 30 minutes.After the reaction, acid-treated graphite is separated by suctionfiltration, and a cleaning operation is repeated twice in which theacid-treated graphite is agitated in 300 parts by weight of water for 10minutes and is then subjected to suction filtration, therebysufficiently removing the sulfuric acid content from the acid-treatedgraphite. Then, the acid-treated graphite with the sulfuric acid contentsufficiently removed is dried for 3 hours in a drying furnace held at atemperature of 110° C., and this acid-treated graphite is used as anacid-treated graphite material.

While the acid-treated graphite material is being agitated, theacid-treated graphite material is compounded with a powder or a solutionof an organic phosphorus compound in a predetermined proportion ofamount and is agitated uniformly to obtain a mixture. This mixture issubjected to heating (expansion) treatment for 1 to 10 seconds attemperatures of 950 to 1200° C. to produce cracked gas. The gaps betweengraphite layers are expanded by its gas pressure to form expandedgraphite particles (expansion rate: 200 to 300 times). These expandedgraphite particles are fed to a twin roller apparatus and is subjectedto roll forming, thereby fabricating a heat-resistant expanded graphitesheet having a desired thickness.

<Manufacturing Method: II>

An acid-treated graphite material is fabricated in the same way as inthe above-described manufacturing method I. This acid-treated graphitematerial is subjected to heating (expansion) treatment for 1 to 10seconds at temperatures of 950 to 1200° C. to produce cracked gas. Thegaps between graphite layers are expanded by its gas pressure to formexpanded graphite particles (expansion rate: 200 to 300 times). Theexpanded graphite particles thus obtained are compounded with a powderor a solution of an organic phosphorus compound in a predeterminedproportion of amount and is agitated uniformly to obtain a mixture. Thismixture is fed to a twin roller apparatus and is subjected to rollforming, thereby fabricating a heat-resistant expanded graphite sheethaving a desired thickness.

The heat-resistant expanded graphite sheets fabricated in theabove-described manufacturing methods I and II are flexibleheat-resistant sheet members containing 0.1 to 10.0 wt. % of the organicphosphorus compound and 90.0 to 99.9 wt. % of expanded graphite.

The organic phosphorus compound dispersedly contained in theheat-resistant sheet member exhibits the action of suppressing theoxidative wear of expanded graphite in a high-temperature rangeexceeding 700° C. The content of the organic phosphorus compound is 0.1to 10 wt. %, preferably 0.5 to 7.0 wt. %. The amount of the content ofthe organic phosphorus compound affects the flexibility of theheat-resistant sheet member, and if its content exceeds 10.0 wt. %, theheat-resistant sheet member shows the tendency of becoming hard andbrittle. Therefore, the workability of the sheet member such as bendingin the manufacturing method, which will be described later, is hampered.

The organic phosphorus compound is selected from the group consisting ofan organic phosphonic acid or its ester, an organic phosphinic acid orits ester, a phosphoric ester, a phosphorous ester, a hypophosphorousester, and the like.

As the organic phosphonic acid or its ester, an organic phosphonic acidor its ester which is represented by the following general formula (1)is suitably used:

In the above formula (1), R¹ is an alkyl group having a carbon number of1 to 10, an aryl group having a carbon number of 6 to 18, or an aralkylgroup consisting of an alkylene portion having a carbon number of 1 to10 and an aryl portion having a carbon number of 6 to 18, and each of R²and R³ is a hydrogen atom, an alkyl group having a carbon number of 1 to10, an aryl group having a carbon number of 6 to 18, or an aralkyl groupconsisting of an alkylene portion having a carbon number of 1 to 10 andan aryl portion having a carbon number of 6 to 18.

The alkyl group is a straight-chain or branched-chain alkyl group (e.g.,a methyl group, an ethyl group, a propyl group, an isopropyl group, ann-butyl group, a sec-butyl group, a tert-butyl group, or the like)preferably having a carbon number of 1 to 10, more preferably having acarbon number of 1 to 6. The aryl group is an aryl group (e.g., a phenylgroup, a naphthyl group, an ethylphenyl group, a tolyl group, a xylylgroup, or the like) preferably having a carbon number of 6 to 18, morepreferably having a carbon number of 6 to 10. The aralkyl group is one(e.g., a benzyl group, a naphthylmethyl group, or the like) whosealkylene portion is straight-chain or branched-chain alkylene preferablyhaving a carbon number of 1 to 10, more preferably having a carbonnumber of 1 to 6, and whose aryl portion is aryl preferably having acarbon number of 6 to 18, more preferably having a carbon number of 6 to10.

As specific examples it is possible to cite methylphosphonic acid,ethylphosphonic acid, phenylphosphonic acid, tolylphosphonic acid,benzylphosphonic acid, methylphosphonic acid methyl ester,methylphosphonic acid dimethyl ester, methylphosphonic acid diphenylester, phenylphosphonic acid diethyl ester, and the like.

As the organic phosphinic acid or its ester, an organic phosphinic acidor its ester which is represented by the following general formula (2)is suitably used:

In the above formula (2), R⁴ is an alkyl group or an aryl group, andeach of R⁵ and R⁶ is a hydrogen atom, an alkyl group, or an aryl group.The alkyl group and the aryl group are the same as those describedabove.

As specific examples it is possible to cite methylphosphinic acid,ethylphosphinic acid, diethylphosphinic acid, methylethylphosphinicacid, phenylphosphinic acid, methylphenylphosphinic acid,diphenylphosphinic acid, methylphosphinic acid ethyl ester,dimethylphosphinic acid ethyl ester, methylphosphinic acid phenyl ester,phenylphosphinic acid ethyl ester, and the like.

As the phosphoric ester, a phosphoric ester which is represented by thefollowing general formula (3) is suitably used:

In the above formula (3), each of R⁷, R⁸, and R⁹ is a hydrogen atom, analkyl group, an aryl group, or an aralkyl group, providing that a casewhere all of them are hydrogen atoms is excluded. The alkyl group, thearyl group, and the aralkyl group are the same as those described above.

The alkyl group is a straight-chain or branched-chain alkyl group (e.g.,a methyl group, an ethyl group, a propyl group, an isopropyl group, ann-butyl group, a sec-butyl group, a tert-butyl group, or the like)preferably having a carbon number of 1 to 10, more preferably having acarbon number of 1 to 6. The aryl group is an aryl group (e.g., a phenylgroup, a naphthyl group, an ethylphenyl group, a tolyl group, a xylylgroup, or the like) preferably having a carbon number of 6 to 18, morepreferably having a carbon number of 6 to 10. The aralkyl group is one(e.g., a benzyl group, a naphthylmethyl group, or the like) whosealkylene portion is straight-chain or branched-chain alkylene preferablyhaving a carbon number of 1 to 10, more preferably having a carbonnumber of 1 to 6, and whose aryl portion is aryl preferably having acarbon number of 6 to 18, more preferably having a carbon number of 6 to10.

As specific examples it is possible to cite methyl phosphate, butylphosphate, phenyl phosphate, diethyl phosphate, diphenyl phosphate,benzyl phosphate, trimethyl phosphate, triphenyl phosphate, diphenylcresyl phosphate, methyl diphenyl phosphate, and the like.

As the phosphorous ester, a phosphorous triester which is represented bythe following general formula (4) or a phosphorous diester or aphosphorous monoester which is represented by the following generalformula (5) is suitably used:

In the above formulae (4) and (5), each of R¹⁰, R¹¹, and R¹² is an alkylgroup, an aryl group, or an aralkyl group, and each of R¹³ and R¹⁴ is ahydrogen atom, an alkyl group, an aryl group, or an aralkyl group,providing that a case where both of R¹³ and R¹⁴ are hydrogen atoms isexcluded.

The alkyl group, the aryl group, and the aralkyl group are the same asthose described above. As specific examples it is possible to citetrimethyl phosphite, triphenyl phosphite, diethyl phosphite, diphenylphosphite, butyl phosphite, phenyl phosphite, and the like.

As the hypophosphorous ester, a hypophosphorous diester (phosphonite)which is represented by the following general formula (6) or ahypophosphorous monoester which is represented by the following generalformula (7) is suitably used:

In the above formulae (6) and (7), R¹⁵ is a hydrogen atom, an alkylgroup, an aryl group, or an aralkyl group, and each of R¹⁶, R¹⁷, and R¹⁸is an alkyl group, an aryl group, or an aralkyl group.

The alkyl group, the aryl group, and the aralkyl group are the same asthose described above. As specific examples it is possible to citedimethyl phosphonite, diphenyl phosphonite, dibenzyl phosphonite,diethyl phosphonite, dimethyl phosphonite, methyl hypophosphite, ethylhypophosphite, phenyl hypophosphite, and the like.

<Concerning Reinforcing Member>

As a reinforcing member, a metal wire net is used which is formed byweaving or knitting one or more wire members including, as an iron-basedwire, a stainless steel wire made of such as austenitic stainless steelsSUS 304 and SUS 316, a ferritic stainless steel SUS 430, or an iron wire(JIS-G-3532) or a galvanized iron wire (JIS-G-3547), or, as a copperwire, a wire member made of a copper-nickel alloy (cupro-nickel), acopper-nickel-zinc alloy (nickel silver), brass, or beryllium copper. Asthe wire diameter of the fine metal wire forming the metal wire net, afine metal wire having a diameter of 0.10 to 0.32 mm or thereabouts isused, and a metal wire net whose meshes are 3 to 6 mm or thereabouts issuitably used.

As the reinforcing member, in addition to the above-described metal wirenet, it is also possible to use a so-called expanded metal in which astainless steel sheet or a phosphor bronze sheet is slotted and theslots are expanded to form rows of regular meshes. The thickness of thestainless steel sheet or the phosphor bronze sheet is 0.3 to 0.5 mm orthereabouts, and an expanded metal whose meshes are 3 to 6 mm orthereabouts is suitably used.

<Concerning Lubricating Composition>

An aqueous dispersion containing as a solid content 20 to 50 wt. % of alubricating composition consisting of 70 to 90 wt. % of boron nitrideand 10 to 30 wt. % of at least one of alumina and silica is used. As analternative lubricating composition, an aqueous dispersion is used whichcontains as a solid content 20 to 50 wt. % of a lubricating compositionobtained by allowing a lubricating composition consisting of 70 to 90wt. % of boron nitride and 10 to 30 wt. % of at least one of alumina andsilica to contain not more than 200 parts by weight, preferably 50 to150 parts by weight, of polytetrafluoroethylene resin with respect to100 parts by weight of that lubricating composition.

The above-described aqueous dispersion of the lubricating composition isapplied to the surface of the heat-resistant sheet member by means ofbrushing, roller coating, spraying, or the like in the manufacturingmethod which will be described later, and is used so as to form alubricating sliding layer on the surface of the heat-resistant sheet bycoating the surface of the heat-resistant sheet. In a final compressionprocess, the lubricating sliding layer thus formed is spread into auniform and very small thickness (10 to 300 μm) to form an outer surfacelayer on the partially convex spherical outer surface and its vicinitiesof the spherical annular seal member.

Boron nitride among the aforementioned lubricating compositionsdemonstrates excellent lubricity particularly at high temperatures.However, boron nitride as a single constituent is inferior in itsadhesion onto the surface of the heat-resistant sheet and, hence, in itsadhesion onto the partially convex spherical outer surface of thespherical annular base member in the final compression process.Consequently, boron nitride as a single constituent has a drawback inthat it is easily exfoliated from these surfaces. However, bycompounding at least one of alumina and silica with boron nitride at afixed ratio, it is possible to avoid the aforementioned drawback ofboron nitride, substantially improve its adhesion onto the surface ofthe heat-resistant sheet and, hence, onto the partially convex sphericalsurface of the spherical annular base member in the final compressionprocess, and enhance the retention of the partially convex sphericalouter surface and constituting the lubricating sliding surface formed ofthe lubricating composition in the outer layer of the spherical annularseal member. The proportion in which at least one of alumina and silicais compounded with respect to boron nitride is determined from theviewpoint of improving adhesion without impairing the lubricity of boronnitride, and a range of 10 to 30 wt. % is therefore preferable.

In the aforementioned lubricating composition which contains thelubricating composition consisting of 70 to 90 wt. % of boron nitrideand 10 to 30 wt. % of at least one of alumina and silica, and furthercontains polytetrafluoroethylene resin at a fixed ratio with respect to100 parts by weight of this lubricating composition,polytetrafluoroethylene resin itself has a low frictional property, andas it is compounded with the lubricating composition formed of boronnitride and at least one of alumina and silica, polytetrafluoroethyleneresin exhibits the action of improving the low frictional property ofthe lubricating composition and the action of enhancing the ductility ofthe lubricating composition during compression forming.

The proportion in which polytetrafluoroethylene resin is compounded withrespect to 100 parts by weight of the lubricating composition of 70 to90 wt. % of boron nitride and 10 to 30 wt. % of at least one of aluminaand silica is not more than 200 parts by weight, preferably in the rangeof 50 to 150 parts by weight. If the compounding proportion ofpolytetrafluoroethylene resin exceeds 200 parts by weight, theproportion of the resin in the lubricating composition becomes large,thereby resulting in a decline in the heat resistance of the lubricatingcomposition. If the compounding proportion of polytetrafluoroethyleneresin is in the range of 50 to 150 parts by weight, the low frictionalproperty can be demonstrated most satisfactorily without impairing theheat resistance of the lubricating composition. As thispolytetrafluoroethylene resin, an aqueous dispersion dispersedlycontaining as a solid content 30 to 50 wt. % of a fine powder with anaverage particle size of 10 μm or less.

Next, referring to the drawings, a description will be given of themethod of manufacturing the spherical annular seal member composed ofthe above-described constituent materials.

<Manufacturing Method in Accordance with First Embodiment>

(First Process) As shown in FIG. 2, a tubular metal wire net 1 formed byknitting fine metal wires into a cylindrical shape is passed betweenrollers 2 and 3, thereby fabricating a belt-shaped metal wire net 4having a predetermined width D. A reinforcing member 5 obtained bycutting the belt-shaped metal wire net 4 into a predetermined length L,or a reinforcing member 5 obtained by cutting a belt-shaped metal wirenet 4, which is formed directly by knitting or the like, into thepredetermined width D and length L, is prepared.

(Second Process) As shown in FIG. 3, a heat-resistant sheet member 6 isprepared which contains 0.1 to 10.0 wt. % of the organic phosphoruscompound and 90.0 to 99.9 wt. % of expanded graphite and has been cut soas to have a width d of 1.1×D to 2.1×D with respect to the width D ofthe reinforcing member 5 and a length l of 1.30×L to 2.70×L with respectto the length L of the reinforcing member 5.

(Third Process) A superposed assembly 12 in which the reinforcing member5 and the heat-resistant sheet member 6 are superposed one on top of theother is prepared as follows: To ensure that the heat-resistant materialis wholly exposed on at least one axial end side of a partially convexspherical surface 53 in a spherical annular seal member 58, which willbe described later (see FIG. 1), i.e., on a large-diameter-side end face54 which is an annular end face, the heat-resistant sheet member 6 ismade to project in the widthwise direction by a maximum of 0.1×D to0.8×D from at least one widthwise end 7 of the reinforcing member 5,which becomes the large-diameter-side end face 54 of the partiallyconvex spherical surface 53. Also, the amount of widthwise projection,61, of the heat-resistant sheet member 6 from the end 7 becomes greaterthan the amount of its widthwise projection, 62, from the otherwidthwise end 8 of the reinforcing member 5, which becomes asmall-diameter side annular end face 55 of the partially convexspherical surface 53. Also, the heat-resistant sheet member 6 is made toproject in the longitudinal direction by a maximum of 0.30×L to 1.70×Lfrom at one longitudinal end 9 of the reinforcing member 5. Also, theother longitudinal end 10 of the reinforcing member 5 and a longitudinalend 11 of the heat-resistant sheet member 6 corresponding to that end 10are made to substantially agree with each other. The reinforcing member5 and the heat-resistant sheet member 6 are thus matched in thewidthwise direction and the longitudinal direction.

(Fourth Process) As shown in FIG. 5, the superposed assembly 12 isconvoluted with the heat-resistant sheet member 6 placed on the innerside such that heat-resistant sheet member 6 is convoluted with one moreturn, thereby forming a tubular base member 13 in which theheat-resistant sheet member 6 is exposed on both the inner peripheralside and the outer peripheral side. As the heat-resistant sheet member6, one is prepared in advance which has a length l of 1.30×L to 2.70×Lwith respect to the length L of the reinforcing member 5 so that thenumber of winding turns of the heat-resistant sheet member 6 in thetubular base member 13 becomes greater than the number of winding turnsof the reinforcing member 5. In the tubular base member 13, as shown inFIG. 6, the heat-resistant sheet member 6 on its one widthwise end sideprojects in the widthwise direction by δ1 from the one end 7 of thereinforcing member 5, and the heat-resistant sheet member 6 on its otherwidthwise end side projects in the widthwise direction by δ2 from theother end 8 of the reinforcing member 5.

(Fifth Process) Another heat-resistant sheet member 6, which is similarto the above-described heat-resistant sheet member 6 but has a smallerwidth d than the width D and a length l of such a measure as to becapable of being wound around the tubular base member 13 by one turn, isprepared separately, as shown in FIG. 7. Meanwhile, as described in theabove-described first process, after the fine metal wires are woven toform the cylindrical metal wire net 1, another reinforcing member 5constituted by the belt-shaped metal wire net 4, which is fabricated byallowing the cylindrical metal wire net 1 to be passed between therollers 3 and 4, is prepared separately. Subsequently, as shown in FIG.8, the heat-resistant sheet member 6 is inserted into the belt-shapedmetal wire net 4, and, as shown in FIG. 9, an assembly thereof is passedbetween rollers 14 and 15 so as to be formed integrally, therebypreparing an outer-surface-layer forming member 16.

(Sixth Process) The outer-surface-layer forming member 16 thus obtainedis wound around an outer peripheral surface of the aforementionedtubular base member 13, thereby preparing a cylindrical preform 17, asshown in FIG. 10.

(Seventh Process) As shown in FIG. 11, a die 37 is prepared which has acylindrical inner wall surface 31, a partially concave spherical innerwall surface 32 continuing from the cylindrical inner wall surface 31,and a through hole 33 continuing from the partially concave sphericalinner wall surface 32, and in which a hollow cylindrical portion 35 anda spherical annular hollow portion 36 continuing from the hollowcylindrical portion 35 are formed inside it as a stepped core 34 isinserted in the through hole 33. Then, the cylindrical preform 17 isfitted over the stepped core 34 of the die 37.

The cylindrical preform 17 located in the hollow cylindrical portion 35and the spherical annular hollow portion 36 of the die 37 is subjectedto compression forming under a pressure of 1 to 3 tons/cm² in thedirection of the core axis. Thus, the spherical annular seal member 58is fabricated which includes a spherical annular base member 56 having athrough hole 51 in its central portion and defined by a cylindricalinner surface 52, the partially convex spherical surface 53, and thelarge- and small-diameter-side annular end faces 54 and 55 of thepartially convex spherical surface 53, as well as an outer surface 57formed integrally on the partially convex spherical surface 53 of thespherical annular base member 56, as shown in FIG. 1.

By means of this compression forming, the spherical annular base member56 is constructed so as to be provided with structural integrity as theheat-resistant sheet member 6 and the reinforcing member 5 constitutedby the metal wire net 4 are compressed and intertwined with each other.The spherical annular base member 56 has the reinforcing member 5constituted by the compressed metal wire net 4, as well as theheat-resistant material filling the meshes of the metal wire net 4 ofthis reinforcing member 5, compressed in such a manner as to be formedintegrally with this reinforcing member 5 in mixed form, and containingexpanded graphite and the organic phosphorus compound. The outer layer57 has the heat-resistant material constituted by the compressedheat-resistant sheet member 6 and the reinforcing member 5 constitutedby the metal wire net 4 formed integrally with this heat-resistantmaterial in mixed form. A partially convex spherical outer surface 59exposed to the outside in the outer layer 57 is formed into a smoothsurface, and the heat-resistant material composed of expanded graphiteand the organic phosphorus compound is exposed in the cylindrical innersurface 52.

In the spherical annular seal member fabricated by the above-describedmethod and shown in FIG. 1, the heat-resistant material constituted bythe heat-resistant sheet member 6 is intertwined and formed integrallywith the reinforcing member 5 constituted by the metal wire net 4 whichforms an internal structure, while the partially convex spherical outersurface 59 is formed into a smooth surface in which the heat-resistantmaterial formed by the outer-surface-layer forming member 16 andcomposed of expanded graphite and the organic phosphorus compound, aswell as the reinforcing member 5 constituted by the metal wire net 4,are integrated in mixed form. At the same time, at thelarge-diameter-side annular end face 54 and the small-diameter-side endface 55 of the partially convex spherical surface 53, the heat-resistantsheet member 6 projecting in the widthwise direction of the reinforcingmember 5 is bent and extended, and the heat-resistant material composedof expanded graphite and the organic phosphorus compound is therebyexposed.

It should be noted that, in the above-described second process, theheat-resistant sheet member 6 cut to have a substantially identicallength l with respect to the length L of the reinforcing member 5 isprepared. These members are superposed one on top of the other in thesame way as in the above-described third process to obtain thesuperposed assembly 12. This superposed assembly 12 is formed into thetubular base member 13 with the reinforcing member 5 placed on the innerside in the same way as in the above-described fourth process.Thereafter, the spherical annular seal member 58 is fabricated throughthe fifth process to the seventh process, and the spherical annular sealmember 58 is thereby formed in which the reinforcing member 5constituted by the metal wire net 4 of the spherical annular base member56 is exposed on the cylindrical inner surface 52 in the through hole51.

<Manufacturing Method in Accordance with Second Embodiment>

The first to fourth processes are identical to those of theabove-described first to fourth processes.

(Fifth Process) Another heat-resistant sheet member 6 (see FIG. 7),which is similar to the above-described heat-resistant sheet member 6but has a smaller width d than the width D and a length l of such ameasure as to be capable of being wound around the tubular base member13 by one turn, is prepared separately. An aqueous dispersion containingas a solid content 20 to 50 wt. % of a lubricating compositionconstituted of 70 to 90 wt. % of boron nitride and 10 to 30 wt. % of atleast one of alumina and silica, or an aqueous dispersion which containsas a solid content 20 to 50 wt. % of a lubricating composition obtainedby allowing a lubricating composition consisting of 70 to 90 wt. % ofboron nitride and 10 to 30 wt. % of at least one of alumina and silicato contain not more than 200 parts by weight, preferably 50 to 150 partsby weight, of polytetrafluoroethylene resin with respect to 100 parts byweight of that lubricating composition, is coated on one surface of theheat-resistant sheet member 6 by means of brushing, roller coating,spraying, or the like. This coating is then dried to form a lubricatingsliding layer 18 which is formed of the lubricating composition, asshown in FIG. 12.

The reinforcing member 5 constituted by the belt-shaped metal wire net4, which has been described in the above-described third process, isprepared separately. Subsequently, as shown in FIG. 13, theheat-resistant sheet member 6 having the lubricating sliding layer 18 isinserted into the belt-shaped metal wire net 4, and, as shown in FIG.14, an assembly thereof is passed between rollers 19 and 20 so as to beformed integrally, thereby preparing an outer-surface-layer formingmember 15.

(Sixth Process) The outer-surface-layer forming member 21 thus obtainedis wound around the outer peripheral surface of the aforementionedtubular base member 13 with the lubricating sliding layer 18 placed onthe outer side, thereby preparing a cylindrical preform 22, as shown inFIG. 15. This cylindrical preform 22 is subjected to compression formingin a method similar to that of the above-described seventh process.Thus, the spherical annular seal member 58 is fabricated which includesthe spherical annular base member 56 having the through hole 51 in itscentral portion and defined by the cylindrical inner surface 52, thepartially convex spherical surface 53, and the large- andsmall-diameter-side annular end faces 54 and 55 of the partially convexspherical surface 53, as well as an outer surface 57 formed integrallyon the partially convex spherical surface 53 of the spherical annularbase member 56, as shown in FIGS. 16 and 17. By means of thiscompression forming, the spherical annular base member 56 is constructedso as to be provided with structural integrity as the heat-resistantsheet member 6 and the reinforcing member 5 constituted by the metalwire net 4 are compressed and intertwined with each other. The sphericalannular base member 56 has the reinforcing member 5 constituted by thecompressed metal wire net 4, as well as the heat-resistant materialfilling the meshes of the metal wire net 4 of this reinforcing member 5,compressed in such a manner as to be formed integrally with thisreinforcing member 5 in mixed form, and containing expanded graphite.The outer layer 57 is constructed so as to be provided with structuralintegrity as the lubricating sliding layer 18 and the reinforcing member5 constituted by the metal wire net 4 integrated with that lubricatingsliding layer 18 are compressed and intertwined with each other. Theouter layer 57 has a lubricating composition in which a lubricatingcomposition constituted of 70 to 90 wt. % of boron nitride and 10 to 30wt. % of at least one of alumina and silica, or a lubricatingcomposition consisting of 70 to 90 wt. % of boron nitride and 10 to 30wt. % of at least one of alumina and silica, contains not more than 200parts by weight, preferably 50 to 150 parts by weight, ofpolytetrafluoroethylene resin with respect to 100 parts by weight ofthat lubricating composition, as well as the reinforcing memberconstituted by the metal wire net integrated with this lubricatingcomposition in mixed form. The partially convex spherical outer surface59 exposed to the outside in the outer layer 57 is formed into a smoothsurface in which the aforementioned lubricating composition and thereinforcing member are integrated in mixed form. The cylindrical innersurface 52 defining the through hole 51 is formed as a surface in whichthe compressed heat-resistant sheet member 6 is exposed, with the resultthat the heat-resistant material composed of expanded graphite and theorganic phosphorus compound in the spherical annular base member 56 isexposed. At the large-diameter-side annular end face 54 and thesmall-diameter-side end face 55 of the partially convex sphericalsurface 53, the heat-resistant sheet member 6 projecting in thewidthwise direction of the reinforcing member 5 is bent and extended,and the heat-resistant material composed of expanded graphite and theorganic phosphorus compound is thereby exposed.

In the above-described second manufacturing method as well, in thesecond process, the heat-resistant sheet member 6 having a substantiallyidentical length l with respect to the length L of the reinforcingmember 5 is prepared. These members are superposed one on top of theother in the same way as described above to obtain the superposedassembly 12. This superposed assembly 12 is formed into the tubular basemember 13 with the reinforcing member 5 placed on the inner side in thesame way as described above. The spherical annular seal member 58 isformed from this tubular base member 13, and the spherical annular sealmember 58 is thereby formed in which the reinforcing member 5constituted by the metal wire net 4 of the spherical annular base member56 is exposed on the cylindrical inner surface 52 in the through hole51.

The spherical annular seal member 58 is used by being incorporated inthe exhaust pipe spherical joint shown in FIG. 18, for example. That is,a flange 200 is provided uprightly on an outer peripheral surface of anupstream-side exhaust pipe 100, which is connected to an engine, byleaving a pipe end 101. The spherical annular seal member 58 is fittedover the pipe end 101 at the cylindrical inner surface 52 defining thethrough hole 51, and is seated with its large-diameter-side end face 54abutting against that flange 200. A downstream-side exhaust pipe 300opposes at one end the upstream-side exhaust pipe 100 and is connectedat the other end to a muffler. A flared portion 301, which is comprisedof a concave spherical surface portion 302 and a flange portion 303provided at a rim of an opening portion of the concave spherical surfaceportion 302, is formed integrally at one end of the downstream-sideexhaust pipe 300. The exhaust pipe 300 is disposed with the concavespherical surface portion 302 slidingly abutting against the partiallyconvex spherical outer surface 59 of the spherical annular seal member58.

In the exhaust pipe spherical joint shown in FIG. 18, thedownstream-side exhaust pipe 300 is constantly urged resiliently towardthe upstream-side exhaust pipe 100 by means of a pair of bolts 400 eachhaving one end fixed to the flange 200 and another end arranged by beinginserted in the flange portion 303 of the flared portion 301, and bymeans of a pair of coil springs 500 each arranged between an enlargedhead of the bolt 400 and the flange portion 303. The exhaust pipespherical joint is arranged such that relative angular displacementsoccurring in the upstream- and downstream-side exhaust pipes 100 and 300are allowed by sliding contact between the partially convex sphericalouter surface 59 of the spherical annular seal member 58 and the concavespherical surface portion 302 of the flared portion 301 formed at theend of the downstream-side exhaust pipe 300.

Next, the present invention will be described in detail in accordancewith examples. It should be noted that the present invention is notlimited to these examples.

EXAMPLES Examples 1 to 8

While 300 parts by weight of concentrated sulfuric acid with aconcentration of 98% was being agitated, 5 parts by weight of a 60%aqueous solution of hydrogen peroxide was added as an oxidizer, and thiswas used as a reaction liquid. This reaction liquid was cooled and heldat a temperature of 10° C., 100 parts by weight of a scaly naturalgraphite powder with a particle size of 30 to 80 meshes was added tothis reaction liquid, and reaction was allowed to take place for 30minutes. After the reaction, the acid-treated graphite was separated bysuction and filtration, and a cleaning operation in which theacid-treated graphite was agitated in 300 parts by weight of water for10 minutes and was sucked and filtered was repeated two times, therebysufficiently removing the sulfuric acid content from the acid-treatedgraphite. Next, the acid-treated graphite from which the sulfuric acidcontent was removed sufficiently was dried for three hours in a dryingfurnace held at a temperature of 110° C., and this was used as theacid-treated graphite material.

While 100 parts by weight of the acid-treated graphite material wasbeing agitated, the acid-treated graphite material was compounded with(1) 0.1 parts by weight, (2) 0.5 parts by weight, (3) 1.0 parts byweight, (4) 2.0 parts by weight, (5) 4.2 parts by weight, (6) 6.4 partsby weight, (7) 8.7 parts by weight, and (8) 11.1 parts by weight,respectively, of a powder of phenylphosphonic acid as the organicphosphorus compound, and was agitated uniformly, thereby obtaining 8kinds of mixtures. These mixtures were subjected to heating treatmentfor 5 seconds at a temperature of 1000° C. to produce cracked gas. Thegaps between graphite layers were expanded by its gas pressure, therebyobtaining expanded graphite particles having an expansion rate of 240times. In this expansion treatment process, the phenylphosphonic acidamong the components was dispersedly contained in the expanded graphiteparticles. These expanded graphite particles were subjected to rollforming by being passed through a reduction roll, thereby fabricatingexpanded graphite sheets having a thickness of 0.38 mm. These sheetswere used as the heat-resistant sheet members 6. These heat-resistantsheet members 6 respectively contained (1) 0.1% by weight ofphenylphosphonic acid and 99.9% by weight of expanded graphite, (2) 0.5%by weight of phenylphosphonic acid and 99.5% by weight of expandedgraphite, (3) 1.0% by weight of phenylphosphonic acid and 99.0% byweight of expanded graphite, (4) 2.0% by weight of phenylphosphonic acidand 98.0% by weight of expanded graphite, (5) 4.0% by weight ofphenylphosphonic acid and 96.0% by weight of expanded graphite, (6) 6.0%by weight of phenylphosphonic acid and 94.0% by weight of expandedgraphite, (7) 8.0% by weight of phenylphosphonic acid and 92.0% byweight of expanded graphite, and (8) 10.0% by weight of phenylphosphonicacid and 90.0% by weight of expanded graphite.

The heat-resistant sheet members 6 thus fabricated and constituted ofthe above-described component compositions (1) to (8) were respectivelycut into a width of 52 mm and a length of 655 mm.

By using two austenitic stainless steel wires (SUS 304) having a wirediameter of 0.28 mm as fine metal wires, a cylindrical woven metal wirenet whose meshes were 4.0 mm was fabricated and was passed between therollers 2 and 3 to form the belt-shaped metal wire net 4 with a width of35 mm and a length of 320 mm. This metal wire net 4 was used as thereinforcing member 5.

After each of the aforementioned heat-resistant sheet members 6 cut intothe width of 52 mm and the length of 655 mm was convoluted around theouter peripheral surface of the core with a diameter of 45 mm by aone-circumference portion, the reinforcing member 5 was superposed onthe inner side of the heat-resistant sheet member 6, and the superposedassembly thereof was convoluted, thereby preparing the tubular basemember 13 in which the heat-resistant sheet member 6 was exposed on theoutermost periphery. In this tubular base member 13, widthwise oppositeend portions of the heat-resistant sheet member 6 respectively projectedfrom the reinforcing member 5 in the widthwise direction.

Heat-resistant sheet members 6 having the above-described componentcompositions (1) to (8) were prepared separately, and they wererespectively cut into a width of 48 mm and a length of 193 mm.

By using a fine metal wire similar to the one described above, eachcylindrical woven metal wire net whose meshes were 4.0 mm was formed,and was passed between the pair of rollers 2 and 3, thereby fabricatingthe belt-shaped metal wire net 4 with a width of 52.0 mm and a length of193 mm. Each of the heat-resistant sheet members 6 was inserted intoeach belt-shaped metal wire net 4, and an assembly thereof was passedbetween the pair of rollers 14 and 15 so as to be formed integrally,thereby fabricating the outer-surface-layer forming member 16 in whichthe reinforcing member 5 and the heat-resistant sheet member 6 fillingthe meshes of the reinforcing member 5 and containing phenylphosphonicacid and expanded graphite were present in mixed form.

This outer-surface-layer forming member 16 was wound around the outerperipheral surface of the aforementioned tubular base member 13, therebypreparing the cylindrical preform 17. This cylindrical preform 17 wasfitted over the stepped core 34 of the die 37, and was placed in thespherical annular hollow portion 36 of the die 37 in which the radius ofcurvature of the partially concave spherical inner wall surface 32 was24.5 mm.

The cylindrical preform 17 located in the spherical annular hollowportion 36 of the die 37 was subjected to compression forming under apressure of 2 tons/cm² in the direction of the core axis. Thus, thespherical annular seal member 58 was fabricated which included thespherical annular base member 56 having the through hole 51 in itscentral portion and defined by the cylindrical inner surface 52, thepartially convex spherical surface 53, and the large- andsmall-diameter-side annular end faces 54 and 55 of the partially convexspherical surface 53, as well as the outer surface 57 formed integrallyon the partially convex spherical surface 53 of the spherical annularbase member 56. By means of this compression forming, the sphericalannular base member 56 was constructed so as to be provided withstructural integrity as the heat-resistant sheet member 6 containingphenylphosphonic acid and expanded graphite and the reinforcing member 5constituted by the metal wire net 4 were compressed and intertwined witheach other. The spherical annular base member 56 had the reinforcingmember 5 constituted by the compressed metal wire net 4, as well as theheat-resistant material constituted by the heat-resistant sheet member 6filling the meshes of the metal wire net 4 of this reinforcing member 5and compressed in such a manner as to be formed integrally with thisreinforcing member 5 in mixed form. The outer layer 57 was constructedso as to be provided with structural integrity as the heat-resistantmaterial constituted by the heat-resistant sheet member 6 containingphenylphosphonic acid and expanded graphite, as well as the reinforcingmember 5 constituted by the metal wire net 4 integrated with thisheat-resistant material, were compressed and intertwined with eachother. The partially convex spherical outer surface 59 exposed to theoutside in the outer layer 57 was formed into a smooth surface in whichthe heat-resistant material containing phenylphosphonic acid andexpanded graphite and the reinforcing member 5 were integrated in mixedform. The cylindrical inner surface 52 defining the through hole 51 wasformed as a surface in which the compressed heat-resistant sheet member6 was exposed, with the result that the heat-resistant material formingthe spherical annular base member 56 was exposed. At the annular endfaces 54 and 55, the portions projecting in the widthwise direction fromthe reinforcing member 5 were bent and extended in the heat-resistantsheet member 6, with the result that the annular end faces 54 and 55were covered the heat-resistant material constituted by theheat-resistant sheet member 6.

Examples 9 to 12

The acid-treated graphite material was fabricated in the same way as inthe above-described Examples. While 100 parts by weight of theacid-treated graphite material was being agitated, the acid-treatedgraphite material was compounded with (9) 1.0 parts by weight, (10) 2.0parts by weight, (11) 4.2 parts by weight, and (12) 6.4 parts by weight,respectively, of a powder of phenylphosphonic acid diethyl ester as theorganic phosphorus compound, and was agitated uniformly, therebyobtaining 4 kinds of mixtures. These mixtures were subjected to heatingtreatment for 5 seconds at a temperature of 1000° C. to produce crackedgas. The gaps between graphite layers were expanded by its gas pressure,thereby obtaining expanded graphite particles having an expansion rateof 240 times. In this expansion treatment process, the phenylphosphonicacid diethyl ester was dispersedly contained in the expanded graphiteparticles.

These expanded graphite particles were subjected to roll forming bybeing passed through the reduction roll, thereby fabricating expandedgraphite sheets having a thickness of 0.38 mm. These expanded graphitesheets were used as the heat-resistant sheet members 6. Theseheat-resistant sheet members 6 respectively contained (9) 1.0% by weightof phenylphosphonic acid diethyl ester and 99.0% by weight of expandedgraphite, (10) 2.0% by weight of phenylphosphonic acid diethyl ester and98.0% by weight of expanded graphite, (11) 4.0% by weight ofphenylphosphonic acid diethyl ester and 96.0% by weight of expandedgraphite, and (12) 6.0% by weight of phenylphosphonic acid diethyl esterand 94.0% by weight of expanded graphite.

The heat-resistant sheet members 6 thus fabricated and constituted ofthe above-described component compositions (9) to (12) were respectivelycut into a width of 52 mm and a length of 655 mm.

The reinforcing members 5 each constituted by the metal wire net 4similar to that of the above-described Examples were prepared, and thetubular base members 13 were fabricated by the heat-resistant sheetmember 6 and the reinforcing member 5 in the same way as in theabove-described Examples.

Heat-resistant sheet members 6 having the above-described componentcompositions (9) to (12) were prepared separately, and they wererespectively cut into a width of 48 mm and a length of 193 mm.

In the same way as in the above-described Examples, each cylindricalwoven metal wire net whose meshes were 4.0 mm was formed, and was passedbetween the pair of rollers 2 and 3, thereby fabricating the belt-shapedmetal wire net 4 with a width of 52.0 mm and a length of 193 mm. Each ofthe four kinds of heat-resistant sheet members 6 was inserted into eachbelt-shaped metal wire net 4, and an assembly thereof was passed betweenthe pair of rollers 14 and 15 so as to be formed integrally, therebyfabricating the outer-surface-layer forming member 16 in which thereinforcing member 5 and the heat-resistant sheet member 6 filling themeshes of the reinforcing member 5 and containing phenylphosphonic aciddiethyl ester and expanded graphite were present in mixed form.

Thereafter, in the same way as in the above-described Examples, thespherical annular seal member 58 was fabricated which included thespherical annular base member 56 having the through hole 51 in itscentral portion and defined by the cylindrical inner surface 52, thepartially convex spherical surface 53, and the large- andsmall-diameter-side annular end faces 54 and 55 of the partially convexspherical surface 53, as well as the outer surface 57 formed integrallyon the partially convex spherical surface 53 of the spherical annularbase member 56. By means of this compression forming, the sphericalannular base member 56 was constructed so as to be provided withstructural integrity as the heat-resistant sheet member 6 containingphenylphosphonic acid diethyl ester and expanded graphite and thereinforcing member 5 constituted by the metal wire net 4 were compressedand intertwined with each other. The spherical annular base member 56had the reinforcing member 5 constituted by the compressed metal wirenet 4, as well as the heat-resistant material constituted by theheat-resistant sheet member 6 filling the meshes of the metal wire net 4of this reinforcing member 5 and compressed in such a manner as to beformed integrally with this reinforcing member 5 in mixed form. Theouter layer 57 was constructed so as to be provided with structuralintegrity as the heat-resistant material constituted by theheat-resistant sheet member 6 containing phenylphosphonic acid diethylester and expanded graphite, as well as the reinforcing member 5constituted by the metal wire net 4 integrated with this heat-resistantmaterial, were compressed and intertwined with each other. The partiallyconvex spherical outer surface 59 exposed to the outside in the outerlayer 57 was formed into a smooth surface in which the heat-resistantmaterial containing phenylphosphonic acid diethyl ester and expandedgraphite and the reinforcing member 5 were integrated in mixed form. Thecylindrical inner surface 52 defining the through hole 51 was formed asa surface in which the compressed heat-resistant sheet member 6 wasexposed, with the result that the heat-resistant material forming thespherical annular base member 56 was exposed. At the annular end faces54 and 55, the portions projecting in the widthwise direction from thereinforcing member 5 were bent and extended in the heat-resistant sheetmember 6, with the result that the annular end faces 54 and 55 werecovered the heat-resistant material constituted by the heat-resistantsheet member 6.

Examples 13 to 16

The acid-treated graphite material was fabricated in the same way as inthe above-described Examples. While 100 parts by weight of theacid-treated graphite material was being agitated, the acid-treatedgraphite material was compounded with (13) 1.0 parts by weight, (14) 2.0parts by weight, (15) 4.2 parts by weight, and (16) 6.4 parts by weight,respectively, of a powder of diphenylphosphinic acid as the organicphosphorus compound, and was agitated uniformly, thereby obtaining 4kinds of mixtures. These mixtures were subjected to heating treatmentfor 5 seconds at a temperature of 1000° C. to produce cracked gas. Thegaps between graphite layers were expanded by its gas pressure, therebyobtaining expanded graphite particles having an expansion rate of 240times. In this expansion treatment process, the diphenylphosphinic acidamong the components was dispersedly contained in the expanded graphiteparticles.

These expanded graphite particles were subjected to roll forming bybeing passed through the reduction roll, thereby fabricating expandedgraphite sheets having a thickness of 0.38 mm. These expanded graphitesheets were used as the heat-resistant sheet members 6. Theseheat-resistant sheet members 6 respectively contained (13) 1.0% byweight of diphenylphosphinic acid and 99.0% by weight of expandedgraphite, (14) 2.0% by weight of diphenylphosphinic acid and 98.0% byweight of expanded graphite, (15) 4.0% by weight of diphenylphosphinicacid and 96.0% by weight of expanded graphite, and (16) 6.0% by weightof diphenylphosphinic acid and 94.0% by weight of expanded graphite.

The heat-resistant sheet members 6 thus fabricated and constituted ofthe above-described component compositions (13) to (16) wererespectively cut into a width of 52 mm and a length of 655 mm.

The reinforcing members 5 each constituted by the metal wire net 4similar to that of the above-described Examples were prepared, and thetubular base members 13 were fabricated by the heat-resistant sheetmember 6 and the reinforcing member 5 in the same way as in theabove-described Examples.

Heat-resistant sheet members 6 having the above-described componentcompositions (13) to (16) were prepared separately, and they wererespectively cut into a width of 48 mm and a length of 193 mm.

In the same way as in the above-described Examples, each cylindricalwoven metal wire net whose meshes were 4.0 mm was formed, and was passedbetween the pair of rollers 2 and 3, thereby fabricating the belt-shapedmetal wire net 4 with a width of 52.0 mm and a length of 193 mm. Each ofthe four kinds of heat-resistant sheet members 6 was inserted into eachbelt-shaped metal wire net 4, and an assembly thereof was passed betweenthe pair of rollers 14 and 15 so as to be formed integrally, therebyfabricating the outer-surface-layer forming member 16 in which thereinforcing member 5 and the heat-resistant sheet member 6 filling themeshes of the reinforcing member 5 and containing diphenylphosphonicacid and expanded graphite were present in mixed form.

Thereafter, in the same way as in the above-described Examples, thespherical annular seal member 58 was fabricated which included thespherical annular base member 56 having the through hole 51 in itscentral portion and defined by the cylindrical inner surface 52, thepartially convex spherical surface 53, and the large- andsmall-diameter-side annular end faces 54 and 55 of the partially convexspherical surface 53, as well as the outer surface 57 formed integrallyon the partially convex spherical surface 53 of the spherical annularbase member 56. By means of this compression forming, the sphericalannular base member 56 was constructed so as to be provided withstructural integrity as the heat-resistant sheet member 6 containingdiphenylphosphonic acid and expanded graphite and the reinforcing member5 constituted by the metal wire net 4 were compressed and intertwinedwith each other. The spherical annular base member 56 had thereinforcing member 5 constituted by the compressed metal wire net 4, aswell as the heat-resistant material constituted by the heat-resistantsheet member 6 filling the meshes of the metal wire net 4 of thisreinforcing member 5 and compressed in such a manner as to be formedintegrally with this reinforcing member 5 in mixed form. The outer layer57 was constructed so as to be provided with structural integrity as theheat-resistant material constituted by the heat-resistant sheet member 6containing diphenylphosphonic acid and expanded graphite, as well as thereinforcing member 5 constituted by the metal wire net 4 integrated withthis heat-resistant material, were compressed and intertwined with eachother. The partially convex spherical outer surface 59 exposed to theoutside in the outer layer 57 was formed into a smooth surface in whichthe heat-resistant material containing diphenylphosphonic acid andexpanded graphite and the reinforcing member 5 were integrated in mixedform. The cylindrical inner surface 52 defining the through hole 51 wasformed as a surface in which the compressed heat-resistant sheet member6 was exposed, with the result that the heat-resistant material formingthe spherical annular base member 56 was exposed. At the annular endfaces 54 and 55, the portions projecting in the widthwise direction fromthe reinforcing member 5 were bent and extended in the heat-resistantsheet member 6, with the result that the annular end faces 54 and 55were covered the heat-resistant material constituted by theheat-resistant sheet member 6.

Examples 17 to 20

The acid-treated graphite material was fabricated in the same way as inthe above-described Examples. While 100 parts by weight of theacid-treated graphite material was being agitated, the acid-treatedgraphite material was compounded with (17) 1.0 parts by weight, (18) 2.0parts by weight, (19) 4.2 parts by weight, and (20) 6.4 parts by weight,respectively, of a powder of phenylphosphinic acid as the organicphosphorus compound, and was agitated uniformly, thereby obtaining 4kinds of mixtures. These mixtures were subjected to heating treatmentfor 5 seconds at a temperature of 1000° C. to produce cracked gas. Thegaps between graphite layers were expanded by its gas pressure, therebyobtaining expanded graphite particles having an expansion rate of 240times. In this expansion treatment process, the phenylphosphinic acidwas dispersedly contained in the expanded graphite particles.

These expanded graphite particles were subjected to roll forming bybeing passed through the reduction roll, thereby fabricating expandedgraphite sheets having a thickness of 0.38 mm. These expanded graphitesheets were used as the heat-resistant sheet members 6. Theseheat-resistant sheet members 6 respectively contained (17) 1.0% byweight of phenylphosphinic acid and 99.0% by weight of expandedgraphite, (18) 2.0% by weight of phenylphosphinic acid and 98.0% byweight of expanded graphite, (19) 4.0% by weight of phenylphosphinicacid and 96.0% by weight of expanded graphite, and (20) 6.0% by weightof phenylphosphinic acid and 94.0% by weight of expanded graphite.

The heat-resistant sheet members 6 thus fabricated and constituted ofthe above-described component compositions (17) to (20) wererespectively cut into a width of 52 mm and a length of 655 mm.

The reinforcing members 5 each constituted by the metal wire net 4similar to that of the above-described Examples were prepared, and thetubular base members 13 were fabricated by the heat-resistant sheetmember 6 and the reinforcing member 5 in the same way as in theabove-described Examples.

Heat-resistant sheet members 6 having the above-described componentcompositions (17) to (20) were prepared separately, and they wererespectively cut into a width of 48 mm and a length of 193 mm.

In the same way as in the above-described Examples, each cylindricalwoven metal wire net whose meshes were 4.0 mm was formed, and was passedbetween the pair of rollers 2 and 3, thereby fabricating the belt-shapedmetal wire net 4 with a width of 52.0 mm and a length of 193 mm. Each ofthe four kinds of heat-resistant sheet members 6 was inserted into eachbelt-shaped metal wire net 4, and an assembly thereof was passed betweenthe pair of rollers 14 and 15 so as to be formed integrally, therebyfabricating the outer-surface-layer forming member 16 in which thereinforcing member 5 and the heat-resistant sheet member 6 filling themeshes of the reinforcing member 5 and containing phenylphosphonic acidand expanded graphite were present in mixed form.

Thereafter, in the same way as in the above-described Examples, thespherical annular seal member 58 was fabricated which included thespherical annular base member 56 having the through hole 51 in itscentral portion and defined by the cylindrical inner surface 52, thepartially convex spherical surface 53, and the large- andsmall-diameter-side annular end faces 54 and 55 of the partially convexspherical surface 53, as well as the outer surface 57 formed integrallyon the partially convex spherical surface 53 of the spherical annularbase member 56. By means of this compression forming, the sphericalannular base member 56 was constructed so as to be provided withstructural integrity as the heat-resistant sheet member 6 containingphenylphosphonic acid and expanded graphite and the reinforcing member 5constituted by the metal wire net 4 were compressed and intertwined witheach other. The spherical annular base member 56 had the reinforcingmember 5 constituted by the compressed metal wire net 4, as well as theheat-resistant material constituted by the heat-resistant sheet member 6filling the meshes of the metal wire net 4 of this reinforcing member 5and compressed in such a manner as to be formed integrally with thisreinforcing member 5 in mixed form. The outer layer 57 was constructedso as to be provided with structural integrity as the heat-resistantmaterial constituted by the heat-resistant sheet member 6 containingphenylphosphonic acid and expanded graphite, as well as the reinforcingmember 5 constituted by the metal wire net 4 integrated with thisheat-resistant material, were compressed and intertwined with eachother. The partially convex spherical outer surface 59 exposed to theoutside in the outer layer 57 was formed into a smooth surface in whichthe heat-resistant material containing phenylphosphonic acid andexpanded graphite and the reinforcing member 5 were integrated in mixedform. The cylindrical inner surface 52 defining the through hole 51 wasformed as a surface in which the compressed heat-resistant sheet member6 was exposed, with the result that the heat-resistant material formingthe spherical annular base member 56 was exposed. At the annular endfaces 54 and 55, the portions projecting in the widthwise direction fromthe reinforcing member 5 were bent and extended in the heat-resistantsheet member 6, with the result that the annular end faces 54 and 55were covered the heat-resistant material constituted by theheat-resistant sheet member 6.

Examples 21 to 24

The acid-treated graphite material was fabricated in the same way as inthe above-described Examples. While 100 parts by weight of theacid-treated graphite material was being agitated, the acid-treatedgraphite material was compounded with (21) 1.0 parts by weight, (22) 2.0parts by weight, (23) 4.2 parts by weight, and (24) 6.4 parts by weight,respectively, of a powder of a phosphoric ester, specifically diphenylphosphate, as the organic phosphorus compound, and was agitateduniformly, thereby obtaining 4 kinds of mixtures. These mixtures weresubjected to heating treatment for 5 seconds at a temperature of 1000°C. to produce cracked gas. The gaps between graphite layers wereexpanded by its gas pressure, thereby obtaining expanded graphiteparticles having an expansion rate of 240 times. In this expansiontreatment process, the diphenyl phosphate was dispersedly contained inthe expanded graphite particles.

These expanded graphite particles were subjected to roll forming bybeing passed through the reduction roll, thereby fabricating expandedgraphite sheets having a thickness of 0.38 mm. These expanded graphitesheets were used as the heat-resistant sheet members 6. Theseheat-resistant sheet members 6 respectively contained (21) 1.0% byweight of diphenyl phosphate and 99.0% by weight of expanded graphite,(22) 2.0% by weight of diphenyl phosphate and 98.0% by weight ofexpanded graphite, (23) 4.0% by weight of diphenyl phosphate and 96.0%by weight of expanded graphite, and (24) 6.0% by weight of diphenylphosphate and 94.0% by weight of expanded graphite.

The heat-resistant sheet members 6 thus fabricated and constituted ofthe above-described component compositions (21) to (24) wererespectively cut into a width of 52 mm and a length of 655 mm.

The reinforcing members 5 each constituted by the metal wire net 4similar to that of the above-described Examples were prepared, and thetubular base members 13 were fabricated by the heat-resistant sheetmember 6 and the reinforcing member 5 in the same way as in theabove-described Examples.

Heat-resistant sheet members 6 having the above-described componentcompositions (21) to (24) were prepared separately, and they wererespectively cut into a width of 48 mm and a length of 193 mm.

In the same way as in the above-described Examples, each cylindricalwoven metal wire net whose meshes were 4.0 mm was formed, and was passedbetween the pair of rollers 2 and 3, thereby fabricating the belt-shapedmetal wire net 4 with a width of 52.0 mm and a length of 193 mm. Each ofthe four kinds of heat-resistant sheet members 6 was inserted into eachbelt-shaped metal wire net 4, and an assembly thereof was passed betweenthe pair of rollers 14 and 15 so as to be formed integrally, therebyfabricating the outer-surface-layer forming member 16 in which thereinforcing member 5 and the heat-resistant sheet member 6 filling themeshes of the reinforcing member 5 and containing diphenyl phosphate andexpanded graphite were present in mixed form.

Thereafter, in the same way as in the above-described Examples, thespherical annular seal member 58 was fabricated which included thespherical annular base member 56 having the through hole 51 in itscentral portion and defined by the cylindrical inner surface 52, thepartially convex spherical surface 53, and the large- andsmall-diameter-side annular end faces 54 and 55 of the partially convexspherical surface 53, as well as the outer surface 57 formed integrallyon the partially convex spherical surface 53 of the spherical annularbase member 56. By means of this compression forming, the sphericalannular base member 56 was constructed so as to be provided withstructural integrity as the heat-resistant sheet member 6 containingdiphenyl phosphate and expanded graphite and the reinforcing member 5constituted by the metal wire net 4 were compressed and intertwined witheach other. The spherical annular base member 56 had the reinforcingmember 5 constituted by the compressed metal wire net 4, as well as theheat-resistant material constituted by the heat-resistant sheet member 6filling the meshes of the metal wire net 4 of this reinforcing member 5and compressed in such a manner as to be formed integrally with thisreinforcing member 5 in mixed form. The outer layer 57 was constructedso as to be provided with structural integrity as the heat-resistantmaterial constituted by the heat-resistant sheet member 6 containingdiphenyl phosphate and expanded graphite, as well as the reinforcingmember 5 constituted by the metal wire net 4 integrated with thisheat-resistant material, were compressed and intertwined with eachother. The partially convex spherical outer surface 59 exposed to theoutside in the outer layer 57 was formed into a smooth surface in whichthe heat-resistant material containing diphenyl phosphate and expandedgraphite and the reinforcing member 5 were integrated in mixed form. Thecylindrical inner surface 52 defining the through hole 51 was formed asa surface in which the compressed heat-resistant sheet member 6 wasexposed, with the result that the heat-resistant material forming thespherical annular base member 56 was exposed. At the annular end faces54 and 55, the portions projecting in the widthwise direction from thereinforcing member 5 were bent and extended in the heat-resistant sheetmember 6, with the result that the annular end faces 54 and 55 werecovered the heat-resistant material constituted by the heat-resistantsheet member 6.

Examples 25 to 28

The acid-treated graphite material was fabricated in the same way as inthe above-described Examples. While 100 parts by weight of theacid-treated graphite material was being agitated, the acid-treatedgraphite material was compounded by spraying with (25) 1.0 parts byweight, (26) 2.0 parts by weight, (27) 4.2 parts by weight, and (28) 6.4parts by weight, respectively, of a solution of a phosphorous ester,specifically triphenyl phosphite, as the organic phosphorus compound,and was agitated uniformly, thereby obtaining 4 kinds of mixtures. Thesemixtures were subjected to heating treatment for 5 seconds at atemperature of 1000° C. to produce cracked gas. The gaps betweengraphite layers were expanded by its gas pressure, thereby obtainingexpanded graphite particles having an expansion rate of 240 times. Inthis expansion treatment process, the triphenyl phosphite wasdispersedly contained in the expanded graphite particles.

These expanded graphite particles were subjected to roll forming bybeing passed through the reduction roll, thereby fabricating expandedgraphite sheets having a thickness of 0.38 mm. The expanded graphitesheets thus fabricated respectively contained (25) 1.0% by weight oftriphenyl phosphite and 99.0% by weight of expanded graphite, (26) 2.0%by weight of triphenyl phosphite and 98.0% by weight of expandedgraphite, (27) 4.0% by weight of triphenyl phosphite and 96.0% by weightof expanded graphite, and (28) 6.0% by weight of triphenyl phosphite and94.0% by weight of expanded graphite.

The heat-resistant sheet members 6 thus fabricated and constituted ofthe above-described component compositions (25) to (28) wererespectively cut into a width of 52 mm and a length of 655 mm.

The reinforcing members 5 each constituted by the metal wire net 4similar to that of the above-described Examples were prepared, and thetubular base members 13 were fabricated by the heat-resistant sheetmember 6 and the reinforcing member 5 in the same way as in theabove-described Examples.

Heat-resistant sheet members 6 having the above-described componentcompositions (25) to (28) were prepared separately, and they wererespectively cut into a width of 48 mm and a length of 193 mm.

In the same way as in the above-described Examples, each cylindricalwoven metal wire net whose meshes were 4.0 mm was formed, and was passedbetween the pair of rollers 2 and 3, thereby fabricating the belt-shapedmetal wire net 4 with a width of 52.0 mm and a length of 193 mm. Each ofthe four kinds of heat-resistant sheet members 6 was inserted into eachbelt-shaped metal wire net 4, and an assembly thereof was passed betweenthe pair of rollers 14 and 15 so as to be formed integrally, therebyfabricating the outer-surface-layer forming member 16 in which thereinforcing member 5 and the heat-resistant sheet member 6 filling themeshes of the reinforcing member 5 and containing triphenyl phosphiteand expanded graphite were present in mixed form.

Thereafter, in the same way as in the above-described Examples, thespherical annular seal member 58 was fabricated which included thespherical annular base member 56 having the through hole 51 in itscentral portion and defined by the cylindrical inner surface 52, thepartially convex spherical surface 53, and the large- andsmall-diameter-side annular end faces 54 and 55 of the partially convexspherical surface 53, as well as the outer surface 57 formed integrallyon the partially convex spherical surface 53 of the spherical annularbase member 56. By means of this compression forming, the sphericalannular base member 56 was constructed so as to be provided withstructural integrity as the heat-resistant sheet member 6 containingtriphenyl phosphite and expanded graphite and the reinforcing member 5constituted by the metal wire net 4 were compressed and intertwined witheach other. The spherical annular base member 56 had the reinforcingmember 5 constituted by the compressed metal wire net 4, as well as theheat-resistant material constituted by the heat-resistant sheet member 6filling the meshes of the metal wire net 4 of this reinforcing member 5and compressed in such a manner as to be formed integrally with thisreinforcing member 5 in mixed form. The outer layer 57 was constructedso as to be provided with structural integrity as the heat-resistantmaterial constituted by the heat-resistant sheet member 6 containingtriphenyl phosphite and expanded graphite, as well as the reinforcingmember 5 constituted by the metal wire net 4 integrated with thisheat-resistant material, were compressed and intertwined with eachother. The partially convex spherical outer surface 59 exposed to theoutside in the outer layer 57 was formed into a smooth surface in whichthe heat-resistant material containing triphenyl phosphite and expandedgraphite and the reinforcing member 5 were integrated in mixed form. Thecylindrical inner surface 52 defining the through hole 51 was formed asa surface in which the compressed heat-resistant sheet member 6 wasexposed, with the result that the heat-resistant material forming thespherical annular base member 56 was exposed. At the annular end faces54 and 55, the portions projecting in the widthwise direction from thereinforcing member 5 were bent and extended in the heat-resistant sheetmember 6, with the result that the annular end faces 54 and 55 werecovered the heat-resistant material constituted by the heat-resistantsheet member 6.

Examples 29 to 32

The acid-treated graphite material was fabricated in the same way as inthe above-described Examples. While 100 parts by weight of theacid-treated graphite material was being agitated, the acid-treatedgraphite material was compounded with (29) 1.0 parts by weight, (30) 2.0parts by weight, (31) 4.2 parts by weight, and (32) 6.4 parts by weight,respectively, of a powder of a hypophosphorous ester, specificallydimethyl phosphonite, as the organic phosphorus compound, and wasagitated uniformly, thereby obtaining 4 kinds of mixtures. Thesemixtures were subjected to heating treatment for 5 seconds at atemperature of 1000° C. to produce cracked gas. The gaps betweengraphite layers were expanded by its gas pressure, thereby obtainingexpanded graphite particles having an expansion rate of 240 times. Inthis expansion treatment process, the dimethyl phosphonite wasdispersedly contained in the expanded graphite particles.

These expanded graphite particles were subjected to roll forming bybeing passed through the reduction roll, thereby fabricating expandedgraphite sheets having a thickness of 0.38 mm. The expanded graphitesheets thus fabricated respectively contained (29) 1.0% by weight ofdimethyl phosphonite and 99.0% by weight of expanded graphite, (30) 2.0%by weight of dimethyl phosphonite and 98.0% by weight of expandedgraphite, (31) 4.0% by weight of dimethyl phosphonite and 96.0% byweight of expanded graphite, and (32) 6.0% by weight of dimethylphosphonite and 94.0% by weight of expanded graphite.

The heat-resistant sheet members 6 thus fabricated and constituted ofthe above-described component compositions (29) to (32) wererespectively cut into a width of 52 mm and a length of 655 mm.

The reinforcing members 5 each constituted by the metal wire net 4similar to that of the above-described Examples were prepared, and thetubular base members 13 were fabricated by the heat-resistant sheetmember 6 and the reinforcing member 5 in the same way as in theabove-described Examples.

Heat-resistant sheet members 6 having the above-described componentcompositions (29) to (32) were prepared separately, and they wererespectively cut into a width of 48 mm and a length of 193 mm.

In the same way as in the above-described Examples, each cylindricalwoven metal wire net whose meshes were 4.0 mm was formed, and was passedbetween the pair of rollers 2 and 3, thereby fabricating the belt-shapedmetal wire net 4 with a width of 52.0 mm and a length of 193 mm. Each ofthe four kinds of heat-resistant sheet members 6 was inserted into eachbelt-shaped metal wire net 4, and an assembly thereof was passed betweenthe pair of rollers 14 and 15 so as to be formed integrally, therebyfabricating the outer-surface-layer forming member 16 in which thereinforcing member 5 and the heat-resistant sheet member 6 filling themeshes of the reinforcing member 5 and containing dimethyl phosphoniteand expanded graphite were present in mixed form.

Thereafter, in the same way as in the above-described Examples, thespherical annular seal member 58 was fabricated which included thespherical annular base member 56 having the through hole 51 in itscentral portion and defined by the cylindrical inner surface 52, thepartially convex spherical surface 53, and the large- andsmall-diameter-side annular end faces 54 and 55 of the partially convexspherical surface 53, as well as the outer surface 57 formed integrallyon the partially convex spherical surface 53 of the spherical annularbase member 56. By means of this compression forming, the sphericalannular base member 56 was constructed so as to be provided withstructural integrity as the heat-resistant sheet member 6 containingdimethyl phosphonite and expanded graphite and the reinforcing member 5constituted by the metal wire net 4 were compressed and intertwined witheach other. The spherical annular base member 56 had the reinforcingmember 5 constituted by the compressed metal wire net 4, as well as theheat-resistant material constituted by the heat-resistant sheet member 6filling the meshes of the metal wire net 4 of this reinforcing member 5and compressed in such a manner as to be formed integrally with thisreinforcing member 5 in mixed form. The outer layer 57 was constructedso as to be provided with structural integrity as the heat-resistantmaterial constituted by the heat-resistant sheet member 6 containingdimethyl phosphonite and expanded graphite, as well as the reinforcingmember 5 constituted by the metal wire net 4 integrated with thisheat-resistant material, were compressed and intertwined with eachother. The partially convex spherical outer surface 59 exposed to theoutside in the outer layer 57 was formed into a smooth surface in whichthe heat-resistant material containing dimethyl phosphonite and expandedgraphite and the reinforcing member 5 were integrated in mixed form. Thecylindrical inner surface 52 defining the through hole 51 was formed asa surface in which the compressed heat-resistant sheet member 6 wasexposed, with the result that the heat-resistant material forming thespherical annular base member 56 was exposed. At the annular end faces54 and 55, the portions projecting in the widthwise direction from thereinforcing member 5 were bent and extended in the heat-resistant sheetmember 6, with the result that the annular end faces 54 and 55 werecovered the heat-resistant material constituted by the heat-resistantsheet member 6.

Examples 33 to 39

The heat-resistant sheet member 6 and the reinforcing member 5constituted by the metal wire net 4, which were similar to those ofExamples 5, 11, 15, 19, 23, 27, and 31, were prepared, and the tubularbase members 13 were respectively fabricated from the heat-resistantsheet member 6 and the reinforcing member 5 in the same way as in theabove-described Examples.

Heat-resistant sheet members 6 similar to the heat-resistant sheetmembers 6 for forming the aforementioned tubular base members 13 wereprepared separately. An aqueous dispersion (25.5 wt. % of boron nitride,4.5 wt. % of alumina, and 70 wt. % of water) containing as a solidcontent 30 wt. % of a lubricating composition constituted of 85 wt. % ofboron nitride with an average particle size of 7 μm and 15 wt. % ofalumina powder with an average particle size of 0.6 μm was applied byroller coating to one surface of each heat-resistant sheet member 6 cutinto a width of 48 mm and a length of 193 mm, and was then dried. Thiscoating operation was repeated three times to form the lubricatingsliding layer 18 of the lubricating composition.

A belt-shaped metal wire net 4 similar to that of each of theabove-described Examples was prepared, and each heat-resistant sheetmember 6 having the lubricating sliding layer 18 of the lubricatingcomposition was inserted into the belt-shaped metal wire net 4, and anassembly thereof was passed between the pair of rollers 19 and 20 so asto be formed integrally, thereby fabricating the outer-layer formingmember 21 in which the reinforcing member 5 and the lubricatingcomposition of the lubricating sliding layer 18, which filled the meshesof the reinforcing member 5, were present in mixed form on one surfacethereof.

This outer-layer forming member 21 was wound around the outer peripheralsurface of the aforementioned tubular base member 13 with the surface ofthe lubricating sliding layer 18 placed on the outer side, therebypreparing the cylindrical preform 22 in each case. Thereafter, in thesame way as in the above-described Examples, the spherical annular sealmember 58 was fabricated which included the spherical annular basemember 56 having the through hole 51 in its central portion and definedby the cylindrical inner surface 52, the partially convex sphericalsurface 53, and the large- and small-diameter-side annular end faces 54and 55 of the partially convex spherical surface 53, as well as theouter surface 57 formed integrally on the partially convex sphericalsurface 53 of the spherical annular base member 56.

By means of this compression forming, the spherical annular base member57 was constructed so as to be provided with structural integrity as, onthe one hand, one of the heat-resistant sheet member 6 (Example 33)containing phenylphosphonic acid and expanded graphite, theheat-resistant sheet member 6 (Example 34) containing phenylphosphonicacid diethyl ester and expanded graphite, the heat-resistant sheetmember 6 (Example 35) containing diphenylphosphinic acid diethyl esterand expanded graphite, the heat-resistant sheet member 6 (Example 36)containing phenylphosphinic acid diethyl ester and expanded graphite,the heat-resistant sheet member 6 (Example 37) containing diphenylphosphate and expanded graphite, the heat-resistant sheet member 6(Example 38) containing triphenyl phosphite and expanded graphite, andthe heat-resistant sheet member 6 (Example 39) containing dimethylphosphonite and expanded graphite, and, on the other hand, thereinforcing member 5 constituted by the metal wire net 4 were compressedand intertwined with each other. The spherical annular base member 56had the reinforcing member 5 constituted by the compressed metal wirenet 4, as well as the heat-resistant material constituted by theheat-resistant sheet member 6 filling the meshes of the metal wire net 4of this reinforcing member 5 and compressed in such a manner as to beformed integrally with this reinforcing member 5 in mixed form. Theouter layer 57 was constructed so as to be provided with structuralintegrity as the lubricating sliding layer 18 and the reinforcing member5, which was constituted by the metal wire net 4 integrated with thelubricating sliding layer 18, were compressed and intertwined with eachother. The outer layer 57 had the lubricating composition constituted of85 wt. % of boron nitride and 15 wt. % of alumina, as well as thereinforcing member 5 constituted by the metal wire net 4 integrated withthis lubricating composition in mixed form. The partially convexspherical outer surface 59 exposed to the outside in the outer layer 57was formed into a smooth surface in which the lubricating compositionand the reinforcing member 5 were integrated in mixed form. Thecylindrical inner surface 52 defining the through hole 51 was formed asa surface in which the compressed heat-resistant sheet member 6 wasexposed, with the result that the heat-resistant material forming thespherical annular base member 56 was exposed. At the annular end faces54 and 55, the portions projecting in the widthwise direction from thereinforcing member 5 were bent and extended in the heat-resistant sheetmember 6, with the result that the annular end faces 54 and 55 werecovered the heat-resistant material constituted by the heat-resistantsheet member 6.

Examples 40 to 46

The heat-resistant sheet member 6 and the reinforcing member 5constituted by the metal wire net 4, which were similar to those ofExamples 5, 11, 15, 19, 23, 27, and 31, were prepared, and the tubularbase members 13 were respectively fabricated from the heat-resistantsheet member 6 and the reinforcing member 5 in the same way as in theabove-described Examples.

Heat-resistant sheet members 6 similar to the heat-resistant sheetmembers 6 for forming the aforementioned tubular base members 13 wereprepared separately. An aqueous dispersion (17 wt. % of boron nitride, 3wt. % of alumina, 10 wt. % of polytetrafluoroethylene resin, and 70 wt.% of water) containing as a solid content 30 wt. % of a lubricatingcomposition (56.7 wt. % of boron nitride, 10 wt. % of alumina, and 33.3wt. % of polytetrafluoroethylene resin) obtained by allowing alubricating composition constituted of 85 wt. % of boron nitride with anaverage particle size of 7 μm and 15 wt. % of alumina powder with anaverage particle size of 0.6 μm to contain 50 parts by weight of apolytetrafluoroethylene resin powder with an average particle size of0.3 μm with respect to 100 parts by weight of that lubricatingcomposition, was applied by roller coating to one surface of eachheat-resistant sheet member 6 cut into a width of 48 mm and a length of193 mm, and was then dried. This coating operation was repeated threetimes to form the lubricating sliding layer 18 of the lubricatingcomposition.

A belt-shaped metal wire net 4 similar to that of each of theabove-described Examples was prepared, and each heat-resistant sheetmember 6 having the lubricating sliding layer 18 of the lubricatingcomposition was inserted into the belt-shaped metal wire net 4, and anassembly thereof was passed between the pair of rollers 19 and 20 so asto be formed integrally, thereby fabricating the outer-layer formingmember 21 in which the reinforcing member 5 and the lubricatingcomposition of the lubricating sliding layer 18, which filled the meshesof the reinforcing member 5, were present in mixed form on one surfacethereof.

This outer-layer forming member 21 was wound around the outer peripheralsurface of the aforementioned tubular base member 13 with the surface ofthe lubricating sliding layer 18 placed on the outer side, therebypreparing the cylindrical preform 22 in each case. Thereafter, in thesame way as in the above-described Examples, the spherical annular sealmember 58 was fabricated which included the spherical annular basemember 56 having the through hole 51 in its central portion and definedby the cylindrical inner surface 52, the partially convex sphericalsurface 53, and the large- and small-diameter-side annular end faces 54and 55 of the partially convex spherical surface 53, as well as theouter surface 57 formed integrally on the partially convex sphericalsurface 53 of the spherical annular base member 56.

By means of this compression forming, the spherical annular base member57 was constructed so as to be provided with structural integrity as, onthe one hand, one of the heat-resistant sheet member 6 (Example 40)containing phenylphosphonic acid and expanded graphite, theheat-resistant sheet member 6 (Example 41) containing phenylphosphonicacid diethyl ester and expanded graphite, the heat-resistant sheetmember 6 (Example 42) containing diphenylphosphinic acid diethyl esterand expanded graphite, the heat-resistant sheet member 6 (Example 43)containing phenylphosphinic acid diethyl ester and expanded graphite,the heat-resistant sheet member 6 (Example 44) containing diphenylphosphate and expanded graphite, the heat-resistant sheet member 6(Example 45) containing triphenyl phosphite and expanded graphite, andthe heat-resistant sheet member 6 (Example 46) containing dimethylphosphonite and expanded graphite, and, on the other hand, thereinforcing member 5 constituted by the metal wire net 4 were compressedand intertwined with each other. The spherical annular base member 56had the reinforcing member 5 constituted by the compressed metal wirenet 4, as well as the heat-resistant material constituted by theheat-resistant sheet member 6 filling the meshes of the metal wire net 4of this reinforcing member 5 and compressed in such a manner as to beformed integrally with this reinforcing member 5 in mixed form. Theouter layer 57 was constructed so as to be provided with structuralintegrity as the lubricating sliding layer 18 and the reinforcing member5, which was constituted by the metal wire net 4 integrated with thelubricating sliding layer 18, were compressed and intertwined with eachother. The outer layer 57 had the lubricating composition constituted of56.7 wt. % of boron nitride, 10 wt. % of alumina, and 33.3 wt. % ofpolytetrafluoroethylene resin, as well as the reinforcing member 5constituted by the metal wire net 4 integrated with this lubricatingcomposition in mixed form. The partially convex spherical outer surface59 exposed to the outside in the outer layer 57 was formed into a smoothsurface in which the lubricating composition and the reinforcing member5 were integrated in mixed form. The cylindrical inner surface 52defining the through hole 51 was formed as a surface in which thecompressed heat-resistant sheet member 6 was exposed, with the resultthat the heat-resistant material forming the spherical annular basemember 56 was exposed. At the annular end faces 54 and 55, the portionsprojecting in the widthwise direction from the reinforcing member 5 werebent and extended in the heat-resistant sheet member 6, with the resultthat the annular end faces 54 and 55 were covered the heat-resistantmaterial constituted by the heat-resistant sheet member 6.

Comparative Example 1

As the heat-resistant sheet member, an expanded graphite sheet(“Nicafilm (trade name)” made by Nippon Carbon Co., Ltd.) having a widthof 52 mm, a length of 655 mm, and a thickness of 0.4 mm was prepared. Asthe reinforcing member, a belt-shaped metal wire net (35 mm wide and 320mm long) similar to that of the above-described Example 1 was prepared.After the heat-resistant sheet member was convoluted by aone-circumference portion, the reinforcing member was superposed on theinner side of the heat-resistant sheet member, and the superposedassembly thereof was convoluted, thereby preparing a tubular base memberin which the heat-resistant sheet member was located on the outermostperiphery. In this tubular base member, widthwise opposite end portionsof the heat-resistant sheet member respectively projected from thereinforcing member in the widthwise direction.

Another heat-resistant sheet member similar to the aforementionedheat-resistant sheet member was prepared separately, and was cut into awidth of 48 mm and a length of 193 mm. An aqueous dispersion (25.5 wt. %of boron nitride, 4.5 wt. % of alumina, and 70 wt. % of water)containing as a solid content 30 wt. % of a lubricating composition(56.7 wt. % of boron nitride, 10 wt. % of alumina, and 33.3 wt. % ofpolytetrafluoroethylene resin) similar to that of the above-describedExample 30, was applied by roller coating to one surface of thisheat-resistant sheet member, and was then dried. This coating operationwas repeated three times to form the lubricating sliding layer of thelubricating composition.

A belt-shaped metal wire net with a width of 52 mm and a length of 193mm and similar to that of the above-described Example 1 was prepared.The heat-resistant sheet member having the lubricating sliding layer ofthe lubricating composition was inserted into the belt-shaped metal wirenet, and an assembly thereof was passed between the pair of rollers soas to be formed integrally, thereby fabricating the outer-layer formingmember in which the reinforcing member and the lubricating compositionof the lubricating sliding layer, which filled the meshes of thereinforcing member, were present in mixed form. This outer-layer formingmember was wound around the outer peripheral surface of theaforementioned tubular base member with the lubricating sliding layer ofthe lubricating composition placed on the outer side, thereby preparingthe cylindrical preform. Thereafter, the spherical annular seal memberwas fabricated in the same way as in Example 1.

In the spherical annular seal member thus fabricated, the sphericalannular base member was constructed so as to be provided with structuralintegrity as the heat-resistant sheet member and the reinforcing memberconstituted by the metal wire net were compressed and intertwined witheach other. The spherical annular base member had the reinforcing memberconstituted by the compressed metal wire net, as well as theheat-resistant material filling the meshes of the metal wire net of thisreinforcing member and compressed in such a manner as to be formedintegrally with this reinforcing member in mixed form. The outer layerwas constructed so as to be provided with structural integrity as thelubricating sliding layer and the reinforcing member, which wasconstituted by the metal wire net integrated with the lubricatingsliding layer, were compressed and intertwined with each other. Theouter layer had the lubricating composition constituted of 56.7 wt. % ofboron nitride, 10 wt. % of alumina, and 33.3 wt. % ofpolytetrafluoroethylene resin, as well as the reinforcing memberconstituted by the metal wire net integrated with this lubricatingcomposition in mixed form. The partially convex spherical outer surfaceexposed to the outside in the outer layer was formed into a smoothsurface in which the lubricating composition and the reinforcing memberwere integrated in mixed form. The cylindrical inner surface definingthe through hole was formed as a surface in which the compressedheat-resistant sheet member was exposed, with the result that theheat-resistant material forming the spherical annular base member wasexposed. At the annular end faces, the portions projecting in thewidthwise direction from the reinforcing member were bent and extendedin the heat-resistant sheet member, with the result that the annular endfaces were covered the heat-resistant material.

Comparative Example 2

An expanded graphite sheet similar to that of the above-describedComparative Example 1 was prepared. An aqueous solution of aluminumprimary phosphate of a 25% concentration was prepared, and the overallsurfaces of the aforementioned expanded graphite sheet were coated withthis aqueous solution by roller coating, and the thus-coated expandedgraphite sheet was then allowed to dry for 20 minutes at a temperatureof 150° C. in a drying furnace so as to form a heat-resistant coating inan amount of 0.07 g/100 cm² and with a uniform thickness on the overallsurfaces of the expanded graphite sheet. The sheet thus obtained wasused as the heat-resistant sheet member, and this heat-resistant sheetmember was cut into a width of 52 mm and a length of 655 mm.

As the reinforcing member, a belt-shaped metal wire net (35 mm wide and320 mm long) similar to that of the above-described Example 1 wasprepared. After the heat-resistant sheet member was convoluted by aone-circumference portion, this reinforcing member was superposed on theinner side of the heat-resistant sheet member, and the superposedassembly thereof was convoluted, thereby preparing a tubular base memberin which the heat-resistant sheet member was located on the outermostperiphery. In this tubular base member, widthwise opposite end portionsof the heat-resistant sheet member respectively projected from thereinforcing member in the widthwise direction.

Another heat-resistant sheet member similar to the aforementionedheat-resistant sheet member was prepared separately, and was cut into awidth of 48 mm and a length of 193 mm. An aqueous dispersion (25.5 wt. %of boron nitride, 4.5 wt. % of alumina, and 70 wt. % of water)containing as a solid content 30 wt. % of a lubricating composition(56.7 wt. % of boron nitride, 10 wt. % of alumina, and 33.3 wt. % ofpolytetrafluoroethylene resin) similar to that of the above-describedExample 30, was applied by roller coating to one surface of thisheat-resistant sheet member, and was then dried. This coating operationwas repeated three times to form the lubricating sliding layer of thelubricating composition.

A belt-shaped metal wire net with a width of 52 mm and a length of 193mm and similar to that of the above-described Example 1 was prepared.The heat-resistant sheet member having the lubricating sliding layer ofthe lubricating composition was inserted into the belt-shaped metal wirenet, and an assembly thereof was passed between the pair of rollers soas to be formed integrally, thereby fabricating the outer-layer formingmember in which the reinforcing member and the lubricating compositionof the lubricating sliding layer, which filled the meshes of thereinforcing member, were present in mixed form. This outer-layer formingmember was wound around the outer peripheral surface of theaforementioned tubular base member with the lubricating sliding layer ofthe lubricating composition placed on the outer side, thereby preparingthe cylindrical preform. Thereafter, the spherical annular seal memberwas fabricated in the same way as in Example 1.

In the spherical annular seal member thus fabricated, the sphericalannular base member was constructed so as to be provided with structuralintegrity as the heat-resistant sheet member having a heat-resistantcoating constituted of aluminum primary phosphate and the reinforcingmember constituted by the metal wire net were compressed and intertwinedwith each other. The spherical annular base member had the reinforcingmember constituted by the compressed metal wire net, as well as theheat-resistant material filling the meshes of the metal wire net of thisreinforcing member and compressed in such a manner as to be formedintegrally with this reinforcing member in mixed form. The outer layerwas constructed so as to be provided with structural integrity as thelubricating sliding layer and the reinforcing member, which wasconstituted by the metal wire net integrated with the lubricatingsliding layer, were compressed and intertwined with each other. Theouter layer had the lubricating composition constituted of 56.7 wt. % ofboron nitride, 10 wt. % of alumina, and 33.3 wt. % ofpolytetrafluoroethylene resin, as well as the reinforcing memberconstituted by the metal wire net integrated with this lubricatingcomposition in mixed form. The partially convex spherical outer surfaceexposed to the outside in the outer layer was formed into a smoothsurface in which the lubricating composition and the reinforcing memberwere integrated in mixed form. The cylindrical inner surface definingthe through hole was formed as a surface in which the compressedheat-resistant sheet member was exposed, with the result that theheat-resistant coating constituted of aluminum primary phosphate wasexposed. At the annular end faces, the portions projecting in thewidthwise direction from the reinforcing member were bent and extendedin the heat-resistant sheet member, with the result that the annular endfaces were covered the heat-resistant coating constituted of aluminumprimary phosphate.

Comparative Example 3

An expanded graphite sheet similar to that of the above-describedComparative Example 1 was prepared. An aqueous solution of aluminumprimary phosphate of a 25% concentration was prepared, and 5 g ofcalcium fluoride with an average particle size of 4 μm was mixed in 30 gof this aqueous solution, and a mixture was thereby obtained. Theoverall surfaces of the aforementioned expanded graphite sheet werecoated with this mixture by roller coating, and the thus-coated expandedgraphite sheet was then allowed to dry for 20 minutes at a temperatureof 150° C. in a drying furnace so as to form a heat-resistant coating(the weight ratio between calcium fluoride and aluminum primaryphosphate being 1:1.5) with a uniform thickness of 0.3 g/100 cm² on theoverall surfaces of the expanded graphite sheet. The sheet thus obtainedwas used as the heat-resistant sheet member having the heat-resistantcoating, and this heat-resistant sheet member was cut into a width of 52mm and a length of 655 mm.

As the reinforcing member, a belt-shaped metal wire net (35 mm wide and320 mm long) similar to that of the above-described Example 1 wasprepared. After the heat-resistant sheet member was convoluted by aone-circumference portion, this reinforcing member was superposed on theinner side of the heat-resistant sheet member, and the superposedassembly thereof was convoluted, thereby preparing a tubular base memberin which the heat-resistant sheet member was located on the outermostperiphery. In this tubular base member, widthwise opposite end portionsof the heat-resistant sheet member respectively projected from thereinforcing member in the widthwise direction.

Another heat-resistant sheet member similar to the aforementionedheat-resistant sheet member was prepared separately, and was cut into awidth of 48 mm and a length of 193 mm. An aqueous dispersion (25.5 wt. %of boron nitride, 4.5 wt. % of alumina, and 70 wt. % of water)containing as a solid content 30 wt. % of a lubricating composition(56.7 wt. % of boron nitride, 10 wt. % of alumina, and 33.3 wt. % ofpolytetrafluoroethylene resin) similar to that of the above-describedExample 30, was applied by roller coating to one surface of thisheat-resistant sheet member, and was then dried. This coating operationwas repeated three times to form the lubricating sliding layer of thelubricating composition.

A belt-shaped metal wire net with a width of 52 mm and a length of 193mm and similar to that of the above-described Example 1 was prepared.The heat-resistant sheet member having the lubricating sliding layer ofthe lubricating composition was inserted into the belt-shaped metal wirenet, and an assembly thereof was passed between the pair of rollers soas to be formed integrally, thereby fabricating the outer-layer formingmember in which the reinforcing member and the lubricating compositionof the lubricating sliding layer, which filled the meshes of thereinforcing member, were present in mixed form. This outer-layer formingmember was wound around the outer peripheral surface of theaforementioned tubular base member with the lubricating sliding layer ofthe lubricating composition placed on the outer side, thereby preparingthe cylindrical preform. Thereafter, the spherical annular seal memberwas fabricated in the same way as in Example 1.

In the spherical annular seal member thus fabricated, the sphericalannular base member was constructed so as to be provided with structuralintegrity as the heat-resistant sheet member having a heat-resistantcoating constituted of aluminum primary phosphate and calcium fluorideas well as the reinforcing member constituted by the metal wire net werecompressed and intertwined with each other. The spherical annular basemember had the reinforcing member constituted by the compressed metalwire net, as well as the heat-resistant material filling the meshes ofthe metal wire net of this reinforcing member and compressed in such amanner as to be formed integrally with this reinforcing member in mixedform. The outer layer was constructed so as to be provided withstructural integrity as the lubricating sliding layer and thereinforcing member, which was constituted by the metal wire netintegrated with the lubricating sliding layer, were compressed andintertwined with each other. The outer layer had the lubricatingcomposition constituted of 56.7 wt. % of boron nitride, 10 wt. % ofalumina, and 33.3 wt. % of polytetrafluoroethylene resin, as well as thereinforcing member constituted by the metal wire net integrated withthis lubricating composition in mixed form. The partially convexspherical outer surface exposed to the outside in the outer layer wasformed into a smooth surface in which the lubricating composition andthe reinforcing member were integrated in mixed form. The cylindricalinner surface defining the through hole was formed as a surface in whichthe compressed heat-resistant sheet member was exposed, with the resultthat the heat-resistant coating constituted of aluminum primaryphosphate was exposed. At the annular end faces, the portions projectingin the widthwise direction from the reinforcing member were bent andextended in the heat-resistant sheet member, with the result that theannular end faces were covered the heat-resistant coating constituted ofaluminum primary phosphate and calcium fluoride.

With respect to the spherical annular seal members in accordance withthe above-described Examples and Comparative Examples, tests wereconducted on the frictional torque (N·m) for each cycle, the presence orabsence of the occurrence of abnormal noise, and the weight loss (weightreduction) by using the exhaust pipe spherical joint shown in FIG. 18,and its results are discussed below.

<Test Conditions>

-   -   Pressing force using coil springs (spring set force): 706 N    -   Angle of oscillation: ±3°    -   Oscillation frequency: 12 hertz (Hz)    -   Ambient temperature (the outer surface temperature of the        concave spherical surface portion 302 shown in FIG. 18):    -   from room temperature to 720° C.        <Test Method>

After 45,000 oscillating motions are performed at room temperature bysetting an oscillating motion at ±3° at a frequency of 12 Hz as a unitof oscillation, the ambient temperature is raised to a temperature of720° C. while continuing the oscillating motions (the number ofoscillating motions during the temperature rise being 45,000). When theambient temperature reached the temperature of 720° C., 115,000oscillating motions are performed. Finally, the ambient temperature isallowed to drop to room temperature while continuing the oscillatingmotions (the number of oscillating motions during the temperature dropbeing 45,000). The combined total of 250,000 oscillating motions is setas one cycle, and four cycles are performed.

The evaluation of the presence or absence of the occurrence of abnormalfrictional noise was conducted as follows.

-   -   Evaluation Code A: No abnormal frictional noise occurred.    -   Evaluation Code B: Abnormal frictional noise is slightly heard        with the ear brought close to the test piece.    -   Evaluation Code C: Although the noise is generally difficult to        discern from a fixed position (a position 1.5 m distant from the        test piece) since it is blanketed by the noises of the living        environment, the noise can be discerned as abnormal frictional        noise by a person engaged in the test.    -   Evaluation Code D: The noise can be recognized as abnormal        frictional noise (unpleasant sound) by anybody from the fixed        position.

As for the amount of gas leakage (litter/min), an opening of one exhaustpipe 100 connected to the exhaust pipe spherical joint shown in FIG. 18was closed, and dry air was allowed to flow into the joint portion fromthe other exhaust pipe 300 under a pressure of 0.5 kgf/cm². The amountof leakage from the joint portion (sliding contact portions between thepartially convex spherical outer surface 53 of the spherical annularseal member 58 and the flared portion 301, fitting portions between thecylindrical inner surface 52 of the spherical annular seal member 58 andthe pipe end portion 101 of the exhaust pipe 100, and abutting portionsbetween the end face 54 and the flange 200 provided uprightly on theexhaust pipe 100) was measured by means of a flowmeter after testingwith 1,000,000 oscillating motions.

Tables 1 and 2 show the test results of the spherical annular sealmembers 58 in Examples 1 to 8 obtained by the above-described testmethod. Table 3 shows the test results of the spherical annular sealmembers 58 in Examples 9 to 12. Table 4 shows the test results of thespherical annular seal members 58 in Examples 13 to 16. Table 5 showsthe test results of the spherical annular seal members 58 in Examples 17to 20. Table 6 shows the test results of the spherical annular sealmembers 58 in Examples 21 to 24. Table 7 shows the test results of thespherical annular seal members 58 in Examples 25 to 28. Table 8 showsthe test results of the spherical annular seal members 58 in Examples 29to 32. Table 9 shows the test results of the spherical annular sealmembers 58 in Examples 33 to 36. Table 10 shows the test results of thespherical annular seal members 58 in Examples 37 to 39. Table 11 showsthe test results of the spherical annular seal members 58 in Examples 40to 43. Table 12 shows the test results of the spherical annular sealmembers 58 in Examples 44 to 46. Table 13 shows the test results of thespherical annular seal members in Comparative Examples 1 to 3. TABLE 1Examples 1 2 3 4 (Component Composition of Heat-resistant Material)Expanded graphite 99.9 99.5 99.0 98.0 Organic phosphorus compound:Phenylphosphonic acid 0.1 0.5 1.0 2.0 (Test Results) Frictional torque 9.0-12.5  9.1-12.2  9.0-12.3  9.2-12.4 Determination of A-B A-B A-B A-Babnormal frictional noise Weight of seal member 44.9 44.9 45.2 45.1before test Weight of seal member 39.1 39.1 39.8 39.7 after Test Weightreduction rate 13 13 12 12 (%) Amount of gas leakage 0.45 0.43 0.42 0.38

TABLE 2 Examples 5 6 7 8 (Component Composition of Heat-resistantMaterial) Expanded graphite 96.0 94.0 92.0 90.0 Organic phosphoruscompound: Phenylphosphonic acid 4.0 6.0 8.0 10.0 (Test Results)Frictional torque  9.0-11.8  9.1-12.0  9.3-12.2  9.3-12.4 Determinationof A-B A-B A-B A-B abnormal frictional noise Weight of seal member 45.945.6 45.6 45.8 before test Weight of seal member 41.0 40.4 40.3 40.1after Test Weight reduction rate 10.7 11.4 11.6 12.4 (%) Amount of gasleakage 0.32 0.34 0.34 0.38

TABLE 3 Examples 9 10 11 12 (Component Composition of Heat-resistantMaterial) Expanded graphite 99.0 98.0 96.0 94.0 Organic phosphoruscompound: Phenylphosphonic acid 1.0 2.0 4.0 6.0 diethyl ester (TestResults) Frictional torque  9.2-12.3  9.5-12.7  9.0-11.8  9.2-12.0Determination of A-B A-B A-B A-B abnormal frictional noise Weight ofseal member 45.7 45.6 45.6 45.8 before test Weight of seal member 40.240.7 40.8 40.5 after Test Weight reduction rate 12 10.7 10.5 11.6 (%)Amount of gas leakage 0.43 0.40 0.33 0.35

TABLE 4 Examples 13 14 15 16 (Component Composition of Heat-resistantMaterial) Expanded graphite 99.0 98.0 96.0 94.0 Organic phosphoruscompound: Diphenylphosphinic 1.0 2.0 4.0 6.0 acid (Test Results)Frictional torque  9.1-12.2  9.2-12.3  9.0-11.8  9.2-12.0 Determinationof A-B A-B A-B A-B abnormal frictional noise Weight of seal member 45.845.8 45.6 45.6 before test Weight of seal member 40.4 40.7 40.7 40.4after Test Weight reduction rate 11.8 11.1 10.7 11.4 (%) Amount of gasleakage 0.41 0.42 0.34 0.36

TABLE 5 Examples 17 18 19 20 (Component Composition of Heat-resistantMaterial) Expanded graphite 99.0 98.0 96.0 94.0 Organic phosphoruscompound: Phenylphosphinic acid 1.0 2.0 4.0 6.0 (Test Results)Frictional torque  9.1-12.5  9.3-12.2  9.0-11.7  9.2-12.0 Determinationof A-B A-B A-B A-B abnormal frictional noise Weight of seal member 45.845.8 45.6 45.8 before test Weight of seal member 40.3 40.7 40.7 40.4after Test Weight reduction rate 12.0 11.1 10.7 11.8 (%) Amount of gasleakage 0.44 0.42 0.32 0.34

TABLE 6 Examples 21 22 23 24 (Component Composition of Heat-resistantMaterial) Expanded graphite 99.0 98.0 96.0 94.0 Organic phosphoruscompound: (Phosphoric acid ester) Diphenyl phosphate 1.0 2.0 4.0 6.0(Test Results) Frictional torque  9.0-12.3  9.3-12.2  9.0-11.8  9.2-12.2Determination of A-B A-B A-B A-B abnormal frictional noise Weight ofseal member 45.8 45.8 45.6 45.6 before test Weight of seal member 40.440.7 40.7 40.4 after Test Weight reduction rate 11.8 11.1 10.7 11.4 (%)Amount of gas leakage 0.44 0.40 0.34 0.36

TABLE 7 Examples 25 26 27 28 (Component Composition of Heat-resistantMaterial) Expanded graphite 99.0 98.0 96.0 94.0 Organic phosphoruscompound: (Phosphorous acid ester) Triphenyl phosphite 1.0 2.0 4.0 6.0(Test Results) Frictional torque  9.2-12.6  9.3-12.2  9.0-11.8  9.2-12.2Determination of A-B A-B A-B A-B abnormal frictional noise Weight ofseal member 45.6 45.8 45.6 45.8 before test Weight of seal member 40.040.3 40.6 40.5 after Test Weight reduction rate 12.2 12.0 11.0 11.6 (%)Amount of gas leakage 0.46 0.44 0.40 0.38

TABLE 8 Examples 29 30 31 32 (Component Composition of Heat-resistantMaterial) Expanded graphite 99.0 98.0 96.0 94.0 Organic phosphoruscompound: (Hypophosphorous acid ester) Dimethyl phosphonite 1.0 2.0 4.06.0 (Test Results) Frictional torque  9.3-12.6  9.3-12.4  9.0-12.0 9.0-12.4 Determination of A-B A-B A-B A-B abnormal frictional noiseWeight of seal member 45.8 45.6 45.6 45.8 before test Weight of sealmember 40.1 40.1 40.5 40.5 after Test Weight reduction rate 12.4 12.111.2 11.6 (%) Amount of gas leakage 0.48 0.46 0.44 0.40

TABLE 9 Examples 33 34 35 36 (Component Composition of Heat-resistantMaterial) Expanded graphite 96.0 96.0 96.0 96.0 Phenylphosphonic acid4.0 Phenylphosphonic acid 4.0 diethyl ester Diphenylphosphinic 4.0 acidPhenylphosphinic acid 4.0 Diphenyl phosphate Triphenyl phosphiteDimethyl phosphonite (Lubricating Composition of Outer Layer) Boronnitride 85 Alumina 15 (Test Results) Frictional torque 8.0-11.6 8.0-11.88.2-11.6 8.2-12.0 Determination of A A A A abnormal frictional noiseWeight of seal member 46.5 46.3 46.2 46.3 before test Weight of sealmember 41.5 41.4 41.2 41.4 after Test Weight reduction rate 10.8 10.610.8 10.6 (%) Amount of gas leakage 0.32 0.33 0.34 0.35

TABLE 10 Examples 37 38 39 (Component Composition of Heat-resistantMaterial) Expanded graphite 96.0 96.0 96.0 Phenylphosphonic acidPhenylphosphonic acid diethyl ester Diphenylphosphinic acidPhenylphosphinic acid Diphenyl phosphate 4.0 Triphenyl phosphite 4.0Dimethyl phosphonite 4.0 (Lubricating Composition of Outer Layer) Boronnitride 85 Alumina 15 (Test Results) Frictional torque 8.2-11.7 8.4-11.68.4-11.8 Determination of abnormal A A A frictional noise Weight of sealmember 46.4 46.3 46.4 before test Weight of seal member after 41.4 41.241.2 Test Weight reduction rate (%) 10.7 11.0 11.2 Amount of gas leakage0.34 0.38 0.42

TABLE 11 Examples 40 41 42 43 (Component Composition of Heat-resistantMaterial) Expanded graphite 96.0 96.0 96.0 96.0 Phenylphosphonic acid4.0 Phenylphosphonic acid 4.0 diethyl ester Diphenylphosphinic 4.0 acidPhenylphosphinic acid 4.0 Diphenyl phosphate Triphenyl phosphiteDimethyl phosphonite (Lubricating Composition of Outer Layer) Boronnitride 56.7 Alumina 10 PTFE 33.3 (Test Results) Frictional torque7.6-11.6 7.8-11.8 7.9-11.8 8.0-12.0 Determination of A A A A abnormalfrictional noise Weight of seal member 46.5 46.3 46.2 46.3 before testWeight of seal member 41.5 41.4 41.2 41.4 after Test Weight reductionrate 10.8 10.6 10.8 10.6 (%) Amount of gas leakage 0.32 0.33 0.34 0.35In Table 11, PTFE represents polytetrafluoroethylene resin.

TABLE 12 Examples 44 45 46 (Component Composition of Heat-resistantMaterial) Expanded graphite 96.0 96.0 96.0 Phenylphosphonic acidPhenylphosphonic acid diethyl ester Diphenylphosphinic acidPhenylphosphinic acid Diphenyl phosphate 4.0 Triphenyl phosphite 4.0Dimethyl phosphonite 4.0 (Lubricating Composition of Outer Layer) Boronnitride 56.7 Alumina 10 PTFE 33.3 (Test Results) Frictional torque7.8-11.6 7.4-11.6 7.5-11.8 Determination of abnormal A A A frictionalnoise Weight of seal member 46.4 46.3 46.4 before test Weight of sealmember after 41.4 41.2 41.2 Test Weight reduction rate (%) 10.7 11.011.2 Amount of gas leakage 0.34 0.38 0.42In Table 12, PTFE represents polytetrafluoroethylene resin.

TABLE 13 Comparative Examples (Test Results) 1 2 3 Frictional torque7.8-12.0 8.0-11.5 8.1-12.2 Determination of abnormal A A A frictionalnoise Weight of seal member 47.5 47.8 48.2 before test Weight of sealmember after 30.4 34.4 40.9 Test Weight reduction rate (%) 36 28 24Amount of gas leakage 5.8 1.8 1.3

From the weight (g) of the seal member before the test and the weight(g) of the seal member after the test in the test results, it can beappreciated that in the case of the spherical annular seal members inaccordance with the Examples, the weight reduction ratio due to theoxidative wear of expanded graphite making up the seal members was notmore than 13% even under a high-temperature condition exceeding 700° C.,and that the spherical annular seal members in accordance with theExamples exhibit excellent resistance to oxidation in comparison withthe Comparative Examples. In addition, since the heat-resistant sheetmember composed of the organic phosphorus compound and expanded graphitehas flexibility which the ordinary expanded graphite sheet has, it waspossible to effect the bending process in the method of manufacturing aspherical annular seal member without causing any trouble.

1. A spherical annular seal member which is used particularly in anexhaust pipe spherical joint, comprising: a spherical annular basemember defined by a cylindrical inner surface, a partially convexspherical surface, and large- and small-diameter-side annular end facesof said partially convex spherical surface; and an outer layer formedintegrally with said partially convex spherical surface of saidspherical annular base member, said spherical annular base memberincluding a reinforcing member made from a compressed metal wire net anda heat-resistant material filling meshes of said metal wire net of saidreinforcing member, compressed in such a manner as to be formedintegrally with said reinforcing member in mixed form, and containingexpanded graphite and an organic phosphorus compound, said outer layerincluding a heat-resistant material containing expanded graphite and anorganic phosphorus compound, and a reinforcing member constituted by ametal wire net integrated with said heat-resistant material in mixedformed, an outer surface of said partially convex spherical surfaceexposed to an outside in said outer layer being formed into a smoothsurface in which said heat-resistant material and said reinforcingmember are integrated in mixed form.
 2. A spherical annular seal memberwhich is used particularly in an exhaust pipe spherical joint,comprising: a spherical annular base member defined by a cylindricalinner surface, a partially convex spherical surface, and large- andsmall-diameter-side annular end faces of said partially convex sphericalsurface; and an outer layer formed integrally with said partially convexspherical surface of said spherical annular base member, said sphericalannular base member including a reinforcing member made from acompressed metal wire net and a heat-resistant material filling meshesof said metal wire net of said reinforcing member, compressed in such amanner as to be formed integrally with said reinforcing member in mixedform, and containing expanded graphite and an organic phosphoruscompound, said outer layer including a lubricating compositionconstituted of at least boron nitride and at least one of alumina andsilica, and a reinforcing member constituted by a metal wire netintegrated with said lubricating composition in mixed formed, an outersurface of said partially convex spherical surface exposed to an outsidein said outer layer being formed into a smooth lubricating slidingsurface in which said lubricating composition and said reinforcingmember are integrated in mixed form.
 3. A spherical annular seal memberaccording to claim 2, wherein said lubricating composition contains70-90 wt. % of boron nitride and 10-30 wt. % of at least one of aluminaand silica.
 4. A spherical annular seal member according to claim 2 or3, wherein said lubricating composition further containspolytetrafluoroethylene resin.
 5. A spherical annular seal memberaccording to any one of claims 2 to 4, wherein said lubricatingcomposition contains a mixture consisting of 70-90 wt. % of boronnitride and 10-30 wt. % of at least one of alumina and silica, andfurther contains not more than 200 parts by weight ofpolytetrafluoroethylene resin with respect to 100 parts by weight ofsaid mixture.
 6. A spherical annular seal member according to any one ofclaims 2 to 4, wherein said lubricating composition contains a mixtureconsisting of 70-90 wt. % of boron nitride and 10-30 wt. % of at leastone of alumina and silica, and further contains 50 to 150 parts byweight of polytetrafluoroethylene resin with respect to 100 parts byweight of said mixture.
 7. A spherical annular seal member according toany one of claims 1 to 6, wherein said heat-resistant materialcontaining said expanded graphite and said organic phosphorus compoundof said spherical annular base member is exposed on said cylindricalinner surface.
 8. A spherical annular seal member according to any oneof claims 1 to 7, wherein said reinforcing member constituted by saidmetal wire net of said spherical annular base member is exposed on saidcylindrical inner surface.
 9. A spherical annular seal member accordingto any one of claims 1 to 8, wherein said heat-resistant materialcontaining said expanded graphite and said organic phosphorus compoundof said spherical annular base member is exposed on at least one of saidannular end faces.
 10. A spherical annular seal member according to anyone of claims 1 to 9, wherein said heat-resistant material contains 0.1to 10.0 wt. % of said organic phosphorus compound and 90.0 to 99.9 wt. %of said expanded graphite.
 11. A spherical annular seal member accordingto any one of claims 1 to 10, wherein said organic phosphorus compoundis selected from the group consisting of an organic phosphonic acid oran ester thereof, an organic phosphinic acid or an ester thereof, aphosphoric ester, a phosphorous ester, and a hypophosphorous ester. 12.A spherical annular seal member according to claim 11, wherein theorganic phosphonic acid or the ester thereof is represented by thefollowing general formula (1):

wherein R¹ is an alkyl group having a carbon number of 1 to 10, an arylgroup having a carbon number of 6 to 18, or an aralkyl group consistingof an alkylene portion having a carbon number of 1 to 10 and an arylportion having a carbon number of 6 to 18, and each of R² and R³ is ahydrogen atom, an alkyl group having a carbon number of 1 to 10, an arylgroup having a carbon number of 6 to 18, or an aralkyl group consistingof an alkylene portion having a carbon number of 1 to 10 and an arylportion having a carbon number of 6 to
 18. 13. A spherical annular sealmember according to claim 11, wherein the organic phosphonic acid or theester thereof is represented by the following general formula (2):

wherein R⁴ is an alkyl group having a carbon number of 1 to 10, an arylgroup having a carbon number of 6 to 18, or an aralkyl group consistingof an alkylene portion having a carbon number of 1 to 10 and an arylportion having a carbon number of 6 to 18, and each of R⁵ and R⁶ is ahydrogen atom, an alkyl group having a carbon number of 1 to 10, an arylgroup having a carbon number of 6 to 18, or an aralkyl group consistingof an alkylene portion having a carbon number of 1 to 10 and an arylportion having a carbon number of 6 to
 18. 14. A spherical annular sealmember according to claim 11, wherein the phosphoric ester isrepresented by the following general formula (3):

wherein each of R⁷, R⁸, and R⁹ is a hydrogen atom, an alkyl group havinga carbon number of 1 to 10, an aryl group having a carbon number of 6 to18, or an aralkyl group consisting of an alkylene portion having acarbon number of 1 to 10 and an aryl portion having a carbon number of 6to 18, providing that a case where all of them are hydrogen atoms isexcluded.
 15. A spherical annular seal member according to claim 11,wherein the phosphorous ester is selected from a phosphorous triesterwhich is represented by the following general formula (4) and aphosphorous diester or a phosphorous monoester which is represented bythe following general formula (5):

wherein each of R¹⁰, R¹¹, and R¹² is an alkyl group having a carbonnumber of 1 to 10, an aryl group having a carbon number of 6 to 18, oran aralkyl group consisting of an alkylene portion having a carbonnumber of 1 to 10 and an aryl portion having a carbon number of 6 to 18,and each of R¹³ and R¹⁴ is a hydrogen atom, an alkyl group having acarbon number of 1 to 10, an aryl group having a carbon number of 6 to18, or an aralkyl group consisting of an alkylene portion having acarbon number of 1 to 10 and an aryl portion having a carbon number of 6to 18, providing that a case where both of R¹³ and R¹⁴ are hydrogenatoms is excluded.
 16. A spherical annular seal member according toclaim 11, wherein the hypophosphorous ester is a hypophosphorous diester(phosphonite) which is represented by the following general formula (6)or a hypophosphorous monoester which is represented by the followinggeneral formula (7):

herein R¹⁵ is a hydrogen atom, an alkyl group having a carbon number of1 to 10, an aryl group having a carbon number of 6 to 18, or an aralkylgroup consisting of an alkylene portion having a carbon number of 1 to10 and an aryl portion having a carbon number of 6 to 18, and each ofR¹⁶, R¹⁷, and R¹⁸ is an alkyl group having a carbon number of 1 to 10,an aryl group having a carbon number of 6 to 18, or an aralkyl groupconsisting of an alkylene portion having a carbon number of 1 to 10 andan aryl portion having a carbon number of 6 to 18.